A sentence like
We've known each other since 2015
sounds common and normal. However, could you explain the possible circumstances of using a sentence with 2 Present Perfect clauses linked by "since" of this kind:
I've become suicidal again since I've worked here
I've been feeling down since you've been gone
I think I can somehow feel the meaning but I'd appreciate a native speaker's advice.
With regards,
Anabel