I'll back up. Trump's arugment was based on the impeachment clause, which says that first a president is impeached, then a president is tried in the senate, then a president is removed from office, then he is subject to criminal indictment.
The order makes sense, but Trump says if he is not convicted in the Senate and removed, he cannot be prosecuted, which is beyond silly.
Among other things, not all crimes are impeachable, which means a president can get away with them.'
Anyway . . .
3/