They may not be able to fire him and the impeachment process takes a long tinie with an uncertain outcome. The best thing to do is to keep on going with what's happening now. Every time the president makes a public screw up, like getting photographed with two Russian spies and losing control of the pictures so they get seen in the US against his will, getting outed telling them things.
These are major screw ups and each one cuts into his already low approval rating. They must keep happening -- and they surely will considering the president's combination of incompetence and inability to believe he can do or be wrong about anything.
Each incident and the reaction to it must combine to get the message that this man is unsuitable to be president. Public pressure for him to resign and get out of all our way. We don't want him here and an instant replay over and over like commercials for a product removal will, we hope, do the trick soon. Get his approval rating down to low single digits and even he will eventually see the light at the end of his escape hatch.