don't understand lines 9 and 10. What is that supposed to mean?
Line 9 is by 'negation elimination'. From $~q~$ and $~\lnot q~$ you may infer $~\bot~$. The symbol is the contradiction constant, also known as 'falsum' or 'bottom'. (From any statement and its own negation you may infer that you have a contradiction). Some systems call this 'contradiction introduction'.$$\dfrac{q\quad\lnot q}{\bot}{\lnot_\mathsf e}$$
Line 10 is by 'contradiction elimination', also known as 'ex falso quadlibet' or the 'principle of explosion' (or just 'explosion'). "Anything may be derived from a contradiction". So from $\bot$ we may conclude anything, such as $r$.$$\dfrac{\bot}{r}{\bot_\mathsf e}$$
For the second, line 5 is 'negation introduction'. When you derive a contradiction under an assumed position, you may discharge that assumption to deduce the negation of that position. The distinction between this rule and the last is in the discharging of the assumption. $$\dfrac{\dfrac{[\varphi]^\mathrm n\\~~~\vdots}{\bot}}{\lnot \varphi}{{\lnot_\mathsf i}^\mathrm n}$$
Every LEM proof can be rewritten into a double negation elimination proof, and vice versa.
In this case, you can do $$\def\fitch#1#2{~~~~\begin{array}{|l}#1\\\hline #2\end{array}}\fitch{\lnot(\lnot p\vee q)}{\fitch{\lnot p}{\lnot p\vee q\qquad\vee_\mathsf i\\\bot\qquad\lnot_\mathsf e}\\\lnot\lnot p\qquad\lnot_\mathsf i\\p\qquad\lnot\lnot_\mathsf e}\qquad\fitch{\lnot(\lnot p\vee q)}{p\vee\lnot p\qquad\textsf{LEM}\\\fitch{p}{}\\\fitch{\lnot p}{\lnot p\vee q\qquad\vee_\mathsf{i}\\\bot\qquad\lnot_\mathsf e\\p\qquad\bot_\mathsf e}\\p\qquad\vee_\mathsf e}$$
The decision as to which to use is often a choice of style. Here the DNE proof looks more elegant.
Usually though there is not that much difference in complexity. Here's the framework for your first proof, as both DNE and LEM style.
$$\fitch{}{\fitch{\lnot((p\to q)\lor(q\to r))}{\fitch{q}{\fitch{p}{q}\\p\to q\\(p\to q)\lor(q\to r)\\\bot\\r}\\q\to r\\(p\to q)\lor(q\to r)\\\bot}\\\lnot\lnot((p\to q)\lor(q\to r))\\(p\to q)\lor(q\to r)}\quad\fitch{}{q\lor\lnot q\\\fitch{q}{\fitch{p}{q}\\p\to q\\(p\to q)\lor(q\to r)}\\\fitch{\lnot q}{\fitch{q}{\bot\\r}\\q\to r\\(p\to q)\lor(q\to r)}\\(p\to q)\lor(q\to r)}$$