Unable to leave splash screen after "Internal Storage issue"

My Fairphone has a similar issue. See also: Battery problems (wrong charging status / battery might be dying) and Battery problems (wrong charging status / battery might be dying)

I can’t reach the ‘hard reset’ screen either and don’t even reach the splash screen, just the blue lights up when i try to start the phone.
I already contacted support last week, but am still awaiting a reply.

Any suggestions how I could fix it?