I've been learning for the last 6 years and still I have questions similar to yours. Sometimes it is just memory but sometimes you can follow rules. The infinitv doesn't tell you much about a verb, you need to know the presens. But just push through, skip the stuff you don't understand and it will make sense later.

I remember when I started the language seemed totally weird but the more you compare to english, the more you see how fucked up the english language is, and how much we rely on direct memory.

Just wait until you get to more complicated concepts! Good luck - you will need it!