Mouse do I tax the profit?

I regularly take part in tournaments with friends where we often win but get benefits in kind like gaming chairs, monitors, etc. We're, so to speak, newcomers to the esports scene and I want to earn money with it. Do I have to then e.g. If I pay tax on 500 euro winnings in a tournament today? (play warzone with streamers on twitch)

Normal yes.

You should at least state it, you will be in the tax exemption and not have to invest anything, but they always want to know and they want to decide whether you have to pay tax or not.