It could be a silly question. I started learning guitar 2 months ago but the progress are not going very well.
Apart from the previous problem, which I haven't solved yet, I have a problem with the basic strumming of guitar.
For example, in C major, we don't play the 6th string. When I strum upward I can't stop or I stop at the space between the 6th string and 5th string abruptly. I think there is something I am missing.
It's mostly just practise. You should be able to
By "single" I mean, you should be able to do it after concentrating on that very stroke, with time to prepare for it. Both of these strokes can be practised, there's not really much to say about it. I don't find them particularly hard to perform with nails, which from you nylonstring pictures I assume is what you also do; with a pick (which I never use) it's probably a bit harder.
In a fast strumming pattern, there's not really any need for catching all the right strings with an upward stroke: the bass strings are mostly "carrier" notes in such patterns, so it's enough to hit them with each downward stroke, the actual fast rythm is mainly heard from the treble strings, so it's fine if you just concentrate on hitting all the trebles with both up- and downward strokes and maybe also the right bass strings (and when you, accidentally, slightly touch e.g. the A-string in a D-major chord, it's usually also not a big problem), which should again be quite doable, and leave the bass strings a job mainly for the downward strokes.
My answer here may be helpful — if you change the angle of your strum or strum along a curve, you won't need to do any stopping. For something as basic as a C chord I don't think you should need to mute anything.
What is more important than avoiding hitting the 6th string in the case you mention is to avoid sounding the string. As long as you don't hear the string, it doesn't really matter if you strum it or not.
The best way to avoid sounding the 6th string in a C-Maj chord is to let the tip of your 3rd finger rest against the 6th string lightly, almost as if you are pushing it sideways, but without pressure.
This same technique can be used in most cases where you want to mute a given string when strumming.
Work on pick-hand precision - as leftaroundabout mentioned - as well as adjusting your fret-hand fingering to help mute the strings you do not want - as tpburch mentioned. I've not seen any teacher or professional say that one or the other is the exclusive answer. It's usually a combination of both.
All that said, I'm not sure I'd stress over this too much. If you look at the transcriptions, and listen closely to the various performances, you'll see that a lot of artists far more proficient than you and I still end up hitting these "accidentals" now and again (probably not the technically correct usage of that term, but I've heard it too frequently to know of a more accurate term). It doesn't seem to hurt them too much...
I mention this because (at least for me) the more I stressed over this aspect of my strumming technique, the more I hit strings I didn't want. The less I worried about it, focusing instead on what I did want, the less I hit strings I didn't want. Where you place your focus and attention is just as important as how skillfully you can move your hands and fingers.
My advice would be to just go slowly and you'll be able to strum the notes you are trying for. When you are learning it is better to develop good habits than accuracy.
It really doesn't make any difference since you are playing the high E anyway (a C chord is C, E, and G) Low (E),C,E,G,C,E high.
I think that beginners are taught use that chord form because it is an unnatural finger position and fretting the the 3 middle notes is easier.
I usually add the low G when I play a C chord (with my pinky) because it sounds a little better.
Good luck and remember that it just takes time and practice...
For me the easiest way to achieve that is to use your thumb of the left hand to mute the 6th string.
To play the C chord:
Use your third finger (ring finger), which should be on the 5th string, to mute the 6th string. So while your finger presses down on the 5th string, you move it up a little bit so that it just touches the 6th string. This will work well. An alternative is to use your thumb to mute the 6th string but that is harder.
Here is a video showing how to play the C chord in the way I described.
And if you're still learning, I would highly recommend that guy's website. It's free and I've been using it for a while now. He charges for e-books but they're not necessary, I haven't bought any.
When you upstrum you should only hit the highest 3 or 4 strings. Even on an open G chord, for example, I will never even come close to touching the low G or B strings, and I probably won't hit the D string either on an upstrum. If you hit all strings on an upstrum it would sound mechanical and unnatural.
Lots of people have suggested muting the 6th string with a finger / thumb / whatever is sticking out around the requisite area at the time. This is great advice.
After 25 years of playing, I have found this to be something I rely on heavily. I'd also add that it's not always helpful to play all strings on a chord, even all the 'valid' ones. Often it's fine to leave a few strings out, making sure you hit the important ones resoundingly. If you think of it that way, playing a subset of the C chord and either missing or muting the rest starts to look easy and attractive.
Also, I have find ways to play chords such that it suits the strumming style. For example I tend to play C as an A-shape chord, shifted up three frets. I don't play the 1st or 6th string because they're damped by my fingers. This suits me very well- and if I'm borrowing a guitar, sometimes the traditional C shows up weakness in the intonation of the guitar whereas an A chord shape tends not to.
I play a G with my thumb over the 6th string, and a bit extra poking over to mute the A string. Don't need it.. so I don't play it. Purists may throw their hands up in shock. Yeah well .. it leaves the rest of my fingers available for riffs etc while playing a G.
If I'm doing fingerpicking or something that relies on the traditional C chord etc then fine I can do that - but with finger picking it's much easier to miss the strings you don'e want ( that's the whole idea! )
Regarding upstrokes generally: I notice that people very much underestimate the trickiness of the strumming hand. It's easy to concentrate on the fret hand as that's where the detail is, but the strumming is easily important as that's more to do with the way you play whatever notes you've fretted. It's important and not necessarily easy.
Are you missing something ? Really it's down to damping the string(s) you don't want played with a finger etc, and 'aiming' or biasing the strum away from the string you want to miss. Eg on the C chord you mention, to miss the 6th string, aim the strum at the top/middle 3 strings. You'll hit those more forcefully (careful though), and doubtless get a couple of extra ones, meaning maybe you'll probably play all 5 thinner strings, because it's hard to be that precise with regularity. But with muting and this biasing, you should be able to stop the unwanted strings from playing.
As an aside ..
In your pictures of the "Previous Problem" it looks like your guitar has a flat neck nylon-string ? Some guitars (mainly electric or steel strung acoustic) have a curved neck surface so that the middle of each fret is raised. This makes it a bit easier to pick out which strings you want to hit as you strum, as some poke up a bit more than others. It also can make it more difficult to get all 6 though.
On a flatter neck, I can see that you might have some trouble missing some strings when strumming. I just wanted to mention that it's not always that difficult/the same on different guitars.
