[Ethereum] Loading smart contract x with tokens; sending eth to smart contract x; receiving tokens for that eth

Hello dear Eth community,

I am a complete noob, please go easy on me 😉 I am an IT teacher and I want to create a reward system for my class for a game that we play weekly. The game is not blockchain related – basically it is a quiz which when solved would open an ethereum address and an amount of ETH to sent to the address. E.g. “Address is 0x337hj377v..; you can now transfer 2ETH to get your “game reward tokens”.
Once individual sends that ETH, he receives back the appropriate amount of game tokens e.g. 1eth = 0.1 game tokens.

We then count who collected the most and determine the winner.

Again, I am completely new to developing smart contracts and I have some challenges.

I am working on a test net and already created my “game reward tokens”.

Next what I am struggling to do is to create a smart contract which would accept my “game reward tokens” and then would send it to users, to whoever is sending ETH, lets say 1ETH = 10 “game reward tokens”.

So “game reward tokens” >> moved to smart contract address >> sits there until someone sends the ETH. If 1eth sent from address x >> 10 game reward tokens sent to address x.

Is there a change anyone could help me out? Maybe there already were similar discussions and you could point me there.

Would appreciate any suggestions,
Cheers!