I can't understand from here. Why it requires I have ethereum balance too?
You need Ethereum because you probably choose a pair of Ethereum with your token but you can pair your own token to any tokens with value.
For example:
Let’s assume your token ticker is X while you want to pair it with ETH.
You will need same amount of ETH to your own token to create ETH-X token pair.
Traders can either buy your X token with ETH or sell your X token and get ETH in return.
Is there no way just listing and sell my token only?
No, You are creating a trading pair on DEX which means you are obligated to pair your token with other token as means of buying it because you need to supply the initial liquidity for user to buy and sell on your pair.
You are looking for IDO or ICO if you want to sell your token without paring it to any token. You can use pinksale and other launchpad to do that.