SLK200 R171. My centre console between the seats is very difficult to open. You have to use force to get it open and I am scared it breaks.

There is usually a connector (plug) under the seat. A fuse or relay may be bad too. Here is a Google search for fuse and relay diagrams:

https://www.google.com/search?q=2012+Mercedes+SLK200+fuse+relay&client=firefox-b-1&tbm=isch&source=iu&ictx=1&fir=0WxW3syIsY37tM%253A%252CQBVyp7N_t4I3TM%252C_&usg=__639Tmw-v8qpMvXtxYlG0PwsALDo%3D&sa=X&ved=0ahUKEwjztIyGxt_aAhVH_IMKHWtIBdYQ9QEIMTAC#imgrc=Y-mT4CyZkm9P_M:

this situation sounds like an open circuit somewhere. It wont cause a fuse to blow, but where the open can be will be difficult to locate without a wiring diagram.

The rails it runs on are bolted to the floor pan. You can tighten those bolts. Run the seat all the way forward, and you should be able to see the rear bolts from the back seat.
Run the seat all the way back, and you should be able to get to the front bolts.
If they're stripped out, you may have a rust problem.

try lubricating the lock with spray lubricant, let sit for awhile and then carefully work the key back and forth, don't force it as the key could break off. If it seized solid, you will have to replace the lock.

not good m8 you take out the front seats,
undo the two scews in the back of the console , two in the middle at the top side and fight it out ,you need to turn the rear piece to the side difficult this one

I have a 2007 SLK200 can you tell me where and how to adjust the handbrake cables

To replace the console is fairly easy BUT it is time consuming. Assume this is going to take you all day to do.
Remove both front seats. They will possibly be Torx head bolts so you will need a matching socket. Don't use a standard socket as it will chew the bolt head. Disconnect the wiring under the seat for power or heat features. Once the seats are out the middle section should lift free. The dash section is bolted in place to the underside of the dash. Removal is centre first, dash second. Refitting is the other way round.

Baloney! Removing the center console is not difficult but it is beneficial to have step-by-step instructions. Seats do not need to come out but they do need to be moved fore and aft depending on access needs. The trickiest part is getting the console with leather sheath for the parking break off and out. Pull the parking break handle up, lift the console up and work the whole assembly forward and free from the PB handle. Pulling out left and right footwell ductwork is not hard. Putting it back in is a finesse action. German engineers have thought these things through and if something seems extraordinarily difficult, it's usually because you haven't figure out the recipe yet. Buy a shop manual and think it through before acting and you'll be surprised how easy it is. I'll be R&R'ng the heater core on the wife's car and will allow three hours start to finish. However, I've had the heater box in and out of the car for various reasons over the years. Allow six hours if first time. Hope this helps..

they are clipped inside the light so have to use little flat head screw driver to pop it open if old brittle may break but only way to replace the bulb

check by back seat on drivers side