If my erc20 tokens gets a value, How can i convert my erc20 token to ETH?
First of all you must buy at least 0.002 Eth from a friend or anyone else because you cannot do the trade from your ERC20 token into Ethereum.
A friend of mine gave me 0.005 so I am be able to trade my Altcoins into Ethereum and Ethereum into other Altcoins.
The most popular Crypto Exchange if you're owning an ERC20 tokens is EthereDelta and that's supposed to be your first Crypto Exchange because you can't send it to any Crypto Exchange without using Etherdelta.
You should earn first 0.002 Ethereum before doing anything else.