You could phrase it formally as:

Jacek was extremely friendly, professional, and helpful. He was willing to go above and beyond to assist me and ensure I was back on the road as quickly as possible. His support and dedication were greatly appreciated.

Jacek was excellent, he advised that my locking nut was shredded and would need removed . We discussed it and he done it and completed the job.
Excellent job Jacek .would use again .

Jacek was an excellent mechanic. His communication was first class and his attention to detail top drawer. He took the time to explain the process and was in no rush, testing the car fully. Highly recommended

Jacek and his co worker did an amazing job arrive on time explained everything

Very friendly and supportive, would recoment to every customer. Im very happy with their work

Although they resolved several issues with my car, the car still wouldn't start because they informed me that a sensor (NOx) needs to be removed and they couldn't do that here; the car needs to be lifted to complete the job.

But overall, everything went well.

Excellent service will definitely use again on time quick and efficient

Great service. Very professional and got the job done well. Highly recommend.

Yes did a great job thanks 😊
Sorted out my problem told me what the problem was.

Very polite and friendly. This is the second time I have used this service and I can definitely recommend.