opening

It's Nf3, developing a Knight and attacking the e5 black pawn. After that, black should protect it with Nc6 And you have 3 main options: the Italian Game (Bc4) The Spanish Game (Bb5) or the Scotch (d4)

I agree with Nf3 since this knight controls the center.  I play e4 too and I play Nf3 too. It's important to develop the knights and bishops out toward the center.  I hope that this helps.  

One other tip to help you: BEFORE every move, you must ask questions, such as "If I move here, is it safe?, " Can I safely capture a piece?" and more to avoid making silly mistakes.  I offer a free eBook for beginners on how to get better.  www.ChessByLauren.com

Chess Openings Resources for Beginners and Beyond...

https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond

As Black, I play the FRENCH DEFENSE. It is a very solid opening and I always have a plan when I play it. However, depending on how my opponent plays, it can turn into a Sicilian which in general you should avoid playing the Sicilian because there is a lot of theory involved in it but there are only a few Sicilians playable with the french setup