a trader sent me 2 bitcoins on testnet to show that i will receive more after they activate it...I have to pay a certain fee before they activate it
Testnet is a completely separate network, there is no way to ‘activate’ or otherwise move coins between the bitcoin testnet and bitcoin network. Testnet coins are worthless by definition, that is why they are useful to developers who want to test their code without risking funds.
As @redgrittybrick mentioned, you are dealing with a scammer. Do not send them money.