Q: Skoda/VW Intermittent power loss and RPM shooting high - Just after Car Servicing

I own a Skoda Rapid (MT) petrol, 2013 model, 40000 kms done. Recently I got it serviced at a 3rd party service centre and as part of general service, the engine oil, air filter, fuel filter and transmission fluid was changed. All these consumables were bought by me, including the top quality Shell Helix Ultra 5W40 engine oil. They informed me that my clutch is weak and I agreed to it and since the car has run 40k kms, it can happen. But still they told you can drive and thats not a problem. Before the service, my car acceleration and pickup everything was perfect and I didn't feel any lag. Just after the service, I felt that my car loses power after gear shift for a moment, in second gears, I have to accelerate a little bit on the speed breakers, and the rpm is going higher so soon that I need to change gear sooner. RPM would rise to 3-4k, but the speed will remain very less. Earlier I used to go 80+ or even 100kmph on 4th gear, but now since rpm touch redline, I will have to shift to

My car has 8 miles.
My car has a manual transmission.