Simple, good way to move money back and forth in bitcoin?

If possible, I would like to store some of my money in Bitcoin. I’d also like an app where I can see my balance in Bitcoin, and request the conversion of Bitcoin into Euros in my European bank account.

One time I tried a Bitcoin service but there was some video ID and other kind of complicated legal set up. That’s fine but I’m curious if there’s a simpler way to just buy some bitcoin in Euro, then sell it back for Euros? Plus a DIY way to see how much bitcoin you have?

Thanks