Hello everyone

So couple months ago I bought mercedes C220 cdi 2011 facelit, automatic transmission, 180.000 km
Recently I started having some troubles, which I will try to describe

1. Overheating
First time car started to overheat at speed 180 km/h.. I was driving and suddenly I noticed my temperature is at 120°C oops so I put my foot on the brakes and second after temperature went down to normal 90°C and car was acting normally.
Second time it happened at like 155 km/h temperature went to about 100°C so I slowed down, and again almost immediately it dropped to normal, and today I was driving like 140 km/h and temperature started rising again.. so I slowed down and It was normal. When I came home after hour of driving I shut down the car, and openned the hood. And the fan wasnt working? is it normal, on some cars when you shut down the engine. fan goes crazy for next 5 minutes, and Mine was off after little overheating? A/C works perfectly
Driving at like 60-90 km/h for hours did nothing, only when speed is higher.

2. Weird noise
Im hearing weird noise like DUUUUU (booming sound not sure if its correct translation) at speed 90 km/h and 115 km/h once I go slower or faster as those speeds it disappears and the car is quiet again, I tried manual shifting and it doesnt matter what gear Im in the sound is the same. Also I think its not tires, because they are little noisy too but at all speeds.

3. Shaking and noise only in the cabin
Again noise like DUUUU in the cabin, when I sit in the car it shaking and making noise like DUUUU, no matter if Im in P,R,N or D, but in R and D its little little worse. Outside the vehicle its very quiet, engine is quiet, no weird noises,
When Im driving its a lot better I almost dont feel any shakes and no sounds, It happens only when Im not moving. So could be engine or transmission moutings?

4.Hard shifting
It never shifted smoothly, but now its getting little worse sometime, especially between 1-2, 2-3, 3-4 I feel little push, also when slowing down it feels exactly like when you release your clutch very fast on manual transmission. I see there is milion threads about it, but never really find someone saying they have a solution. Fluid change at 105.000 km first time, now it have 180k and not change yet, as mechanic told me he wont garantue to improve shifting after changing atf

Yes I ve read a lot before I decided to create this thread, I ve been reading a lot before I post my self, but I dont really find any solutions.
Im not really car expert, and I also move to another city, so I dont know any reputable mechanic yet, So I better ask you what could it possibly be, so mechanic wont try to scam me for a lot money haha
Excuse me if my english is bad, its not my native langue,

Thanks for every answer

 

@erik186 Overheatonf at high speed suggests a radiator problem, not enough coolant or a water pump problem. For a car as old as yours I would replace the radiator and water pump.