You should be able to pressure wash the rest of that paint off. But some of that wood looks rotted. Is that just a section?
I would start by driving the nails / screws below the surface of the wood. Then power washing to see how much comes up. Check the nails / screws again. You can then use a chemical paint stripper. (eco friendly maybe - please) to get the rest up. Keep the stripper on following the instruction and keeping it lightly misted so it does not dry out. Scrape the rest of the paint off. When all the paint is removed follow the stripper's instructions to neutralize the stripper. Put a deck brightener on it if you will stain it.
When wood gets wet (from power washing / paint stripper) it will swell and may lift some of the nails / screws again. If some do lift again you may just want to pull or unscrew them and replace with a longer nail / screw. The reason is after you apply the stripper where the paint did not come up from power washing you will scrap the gooey softened paint and stripper off. You don't want fasteners (nails / screws) in the way of scrapping or have to scrap around them nor on your knees trying to screw in screws or splattering stripper all over yourself trying to hammer in a nail. Please don't forget eye protection throughout the project. You probably have a bunch of latex gloves leftover from Covid - good time to use when applying chemicals. You want to replace those rotted boards and be careful walking on the boards that are obviously rotted. When you drive the fasteners that have lifted and the wood around it crumbles or the fastener goes right through - replace that board. I found a site where a couple has documented their deck project. They have replaced boards, stripped and applied brightener.
Check it out
HOW TO STRIP A DECK FOR STAIN