I'm new in Nethereum and I only want to transfer ether from account a to account b. Find this big example at Github with a lot of projects in it. I don't unterstand it. So please what is it the easiest way to send a transaction using Nethereum?
It might be hard to understand if you're looking for a structure Ethereum doesn't support. A contract (or a user) can only spend their own funds.
The way to think about this is you set up the contract as an honest middleman. It forwards funds according to the rules. So, the sender sends funds to the contract, and that triggers the contract to do something with the received funds, e.g. forward to the other parties.
Ideally, you break this down into smaller steps. First, record a deposit and the resulting liabilities, then create an on-demand withdrawal function so beneficiaries can claim amounts owed. Although it's possible to forward received funds immediately, there are some security considerations behind the idea of separating deposits and withdrawals.
Hope it helps.