Bravo 1.4 T-jet issues

Hi guys!

New to the forum so pitty on the newbie please.

Just bought a Fiat Bravo 1.4 T-Jet 150hp Sport 2008 with 237000km. As you would guess the car has a little bug here and there but I guess nothing major, or so I hope, but I wonder if its like a standard issue on these cars and how to fix it.

Bug#1
The left side doors in the back and front only open if you pull the handle quickly, while the doors on the other side open normally. Any ideas?

Bug#2
While the car is running there is a small buzzing sound in the cabin and it is coming from under the rear seats right side and it is vibratting a bit. Fuel pump?

Bug#3
While I press the volume up button it sometimes grabs as if I pressed the mute button right next to it but I clearly didnt.

Also heard that the rear speaker is crackling while playing music but I know I have to change it for a new one.

Sorry if I posted in the wrong part of the forum.

THX for all the help upfront