Or is there another way to trade by uniswap with a normal network fee?
Yes, there is. You should download imtoken mobile wallet and import your privatekey that contains your token and ethereum to the imtoken wallet. You must connect it through use wallet connect on uniswap.
On imtoken you will be able to choose how much fees that you will be paid to trade on the uniswap.
Metamask is always facing inaccurate data about the fees and so many people have been complaining about that. Idk what formula that already used by metamask to calculate the average fees.