The first was: "the only thing I've done is created, maybe, the best economy we've had in the history of our country" (source here).
Let's unpack that whopper. First, a President doesn't create an economy. The economy already exists when he or she comes into office. And a sitting President does not have a great deal of influence in making an economy strong (but a President can cause economic weakening, something Trump is risking with his reckless trade wars).
That aside, the economy now is certainly not the strongest in US history. In recent decades, it was stronger under both Bill Clinton and Barack Obama for periods of time. Then again, Trump is a lazy ignoramus who doesn't read, so it's not likely that he has any idea of when the economy was strong and when it wasn't.
The second whopper Trump unloaded was this: "you can't impeach somebody for doing the best job of any president, in the history of our country, for the first two years" (source here).
Well let's see. He only signed one somewhat major piece of legislation that he had almost nothing to do with crafting -- that was the tax code revision. He couldn't deliver on dozens of his grandiose campaign promises, like his boast to deliver a better, cheaper health insurance system. He started a reckless trade war that's dragging down the economy. And he forced the government to shut down for a record length of time and then completely conceded the game when he failed to achieve anything he wanted.
Arguably, Franklin Roosevelt's first two years in office were when a President did the best job in history. But it's not likely that Trump could even name when Roosevelt was President. He's ignorant about history like he's ignorant about many subjects because he's intellectually lazy and refuses to read anything beyond summaries of one or two paragraphs.
One is left wondering why Trump makes such ludicrous statements like the two discussed here. Does he actually believe this tripe? Does he know it's tripe but thinks people will believe it simply because he says it? Or does he even think about what he's doing when he spews nonsense like this -- he could be so conditioned to lying that he no longer even realizes he lies constantly.