'\\' and '\newline' not working

Those two symbols in the tite aren't working and I have no idea what's going on. This is my first time using latex so I'm lost. Also, can someone teach me how to make a bullet like the one in Microsoft Word? Here's my text:

%% logical symbols
% \land     /\
% \lor      \/
% \lnor     (negation)
% \to       ->
% \lequiv   <->
% \models   |=

...

\begin{solution}
$$(P \to (\lnot Q \land R)) \land (P \to \lnot Q)$$
$${With: \hspace{1cm} (\lnot P \lor \lnot Q) \land (\lnot P \lor R) \land (\lnot P \lor \lnot Q)}$$
$${ Without : T1 \lequiv T2 \land T4 \\ – T2 \lequiv P \to T3 \\ – T3 \lequiv \lnot Q \land R \\ – T4 \lequiv P \to \lnot Q \\ – F1 : (T1 \land T2 \land T4) \lor (\lnot T1 \land :T2) \lor (\lnot T1 \land \lnot T4) \\ – F2 : (T2 \land \lnot P) \lor (T2 \land T3) \lor (\lnot T2 \land P \land \lnot T3) \\ – F3 : (T3 \land \lnot Q \land R) \lor (\lnot T3 \land Q) \lor (\lnot T3 \land \lnot R) \\ – F4 : (T4 \land \lnot P) \lor (T4 \land \lnot Q) \lor (\lnot T4 \land P \land Q) \\ Final result: T1 \land F1 \land F2 \land F3 \land F4 }$$
\end{solution}

• Welcome to TeX.SX! Please make your code compilable by adding the documentclass as well as the relevant packages you use. (See also: minimal working example (MWE)) Mar 3, 2021 at 16:26
• Hmmm.... Welcome! LaTeX is a whole different thing than Word. I really advise (if you want to learn LaTeX) going here: learnlatex.org and spend a couple of hour there. It will be time well spent and it will save a lot of time. Mar 3, 2021 at 16:27
• Regarding the "bullet": I guess, you could be interested in using the itemize environment. (\begin{itemize} \item text \end{itemize}). To customize such a list, take a look at the enumitem package. Mar 3, 2021 at 16:27
• More to the point, in math mode (and you shouldn't use $$ in LaTeX anyway) newlines are ignored. And you are mixing an enumerating list and a formula. So it's better to go a bit back to the basics! Good luck! Mar 3, 2021 at 16:28 • Regarding the use of $$, you might want to take a look at: Why is [ … ] preferable to $$…$$? Mar 3, 2021 at 16:38

 is not latex syntax, but if you do use it it is essentially the same as $...$ and that is a single line display, you can not use \\  to get multiple lines.

Use the amsmath package and an align or similar enviornment for multi-line displays.

It was rather hard to guess the intended layout but something like

\documentclass{article}

\usepackage{amsmath,amssymb}
\newcommand\lequiv{\iff}

\begin{document}

\begin{align*}
&(P \to (\lnot Q \land R)) \land (P \to \lnot Q)\\
\text{With}:&\, (\lnot P \lor \lnot Q) \land (\lnot P \lor R) \land (\lnot P \lor \lnot Q)\\
\text{Without}:&\, T1 \lequiv T2 \land T4 \\
&\,T2 \lequiv P \to T3 \\
&\,T3 \lequiv \lnot Q \land R \\
&\,T4 \lequiv P \to \lnot Q \\
F1 :&\, (T1 \land T2 \land T4) \lor (\lnot T1 \land :T2) \lor (\lnot T1 \land \lnot T4) \\
F2 :&\, (T2 \land \lnot P) \lor (T2 \land T3) \lor (\lnot T2 \land P \land \lnot T3) \\
F3 :&\, (T3 \land \lnot Q \land R) \lor (\lnot T3 \land Q) \lor (\lnot T3 \land \lnot R) \\
F4 :&\,(T4 \land \lnot P) \lor (T4 \land \lnot Q) \lor (\lnot T4 \land P \land Q) \\
\text{Final result}:&\, T1 \land F1 \land F2 \land F3 \land F4
\end{align*}
\end{document}