Confusion about matomo

hey there, i have a gaming website my friend told me about matomo, but my question is if i install matomo should i delete google analytics for this?

You have not to delete GA. You can even use some Google tags through Matomo Tag Manager or use some Matomo tags though Google Tag Manager.
But at the end, if you want to be compliant with EU laws, the best is to deactivate Google tags and GTM.
So I would suggest you to follow this: