Please Make timer sound go off even in background!

This app is amazing! I will purchase if the timer sounds will go off in the background and put alert or app itself into the foreground.
Its so odd that it says it will alert user even if app is running in foreground, but I had YouTube running and it did not alert me. It just ended in the background without any alert y or notification. The sound didnt go off nor did a pop up notification did not show :(
My phone was not locked, I just had YouTube running in the foreground.

Sonsiiii about Timer+ · Multiple Timers