Let's start at a high level and forget the rule for now if they are confusing you. All you need to do as a player is direct your character to do what you think they should do at a moment. The DM will be in charge of the world including what you see and how you interact with it.

If the DM says you are in a field and see a single tree. You can decider what you want to do to with the tree. You can chop it down, climb it, identify what type it is etc. Depending on what you say the DM will tell you what to roll to succeed on your task of applicable. This will be usually be a 1d20 plus something usually a skill. So the DM will say you need an Athletic Check to climb a tree. Sometimes a player will combine these and say: "Can I use an acrobatics to climb the tree?" and the DM can redirect "Yes you can climb the tree but you need to use Acrobatics". It's that simple in play

So why so many rules? Do you remember when you were playing imagine as a kid and you said "I hit you with my magic bow so your asleep" and your friend was like "No I got magic super armor that deflects all arrows" and you got into an argument? The rules are to stop that. There are clear definitions of what everything does and does not do. Especially with magic spells which can get tricky.

If the rules are bogging you down, focus only on those that are applicable to you. Play a martial character and ignore all magic rules.

Hope they make sense.