Good luck^^ chess is an interesting world
is it better to learn One opening

It is better to learn one!
Almost everyone on Chess.com plays an opening. The difference is that beginners normally do not play more than 2 or 3 moves of any given opening. Therefor playing an opening that takes 6 moves to reach the normal position makes no sense at all.
You can chose to play e4. Then you need to be ready for e5, d5, and c5. Anything else is not played often enough at the lower levels.
As black you will need to have a plan on what to play in response to e4 and d4.
The biggest reason to play an "opening" is so that you make the same opening moves all of the time, this way. you become familiar with the tactics and possibilities of the positions.
For example I play e4, and if they play d4 I play the Blackmar-Diemer Gambit as follows
Firstly e4 or d4, then moves your knights, keep develop your position until you castling, these are very basic. You may learn different openings one by one, take your time.