I can’t understand one thing about Algorand.
I have a wallet and automatically i am rewarded for “staking” my ALGO.
I can’t understand what is the reward for those are running nodes. Are there any “advantages”, in addition to contributing to the smooth functioning of the network?
As long as you don’t interact with the network frequently, no - there are no gains for running a node.
Howver, if you send lots of transactions, and you want to make sure that your transactions gets the highest priority getting onto the network, running your own node would do that.
Also, running a participation node gives your node the ability to know that you’re not being “played-back” old rounds - again, usually not an issue unless you want to verify the correctness of your node state before sending a transaction.