Perfect

Czy jest możliwe łączenie present perfect z past simple w tego typu zdaniach?

I have been to Warsaw twcie when I was sad.

Zazwyczaj to wiadmo że jest to niepoprawne ale czy są jakieś sytuacjie w których użycie perfect razem z past simple które użyjemy do określenia jakiegoś momentu będzie ok?

A: I’m not happy these days, you know; I feel dejected, spiritless. What do you do when you feel like that?
B: Well. I’ve tried traveling. I have been to Warsaw twice when I felt that way (“sad”would be odd), but it didn’t help.

You are relating your past experience from the present point of view. This usage of the present perfect is called EXPERIENTIAL or RESULTATIVE. “Resultative” means that your recalling the experience of trips to Warsaw (not necessarily their futility) is now relevant and the resultant experience still valid and worth mentioning now.
The present perfect is another stativizer: in any of its uses it yields a state that holds at the moment of speaking.