Check Engine Light On problems of the 2019 Buick Enclave

Note: mileage is 1240 miles, just purchased three months ago with 54 miles on it and shipped to germany (dod civilian). While in europe, I am using the vehicles' "metric" setting (kph versus mph), which switches the speedometer to read kph and auto tunes the engine to the appropriate levels to match kph. I have been driving this vehicle for the last three weeks until the issue happened last night around 1830 hours cet. Issue: while accelerating and tuning left from a stop (stop light with the city), the engine suddenly loss power then jerked into a lower gear, but somehow got stuck in 3rd gear restricting max speed of about 25-30 mph running at 5000 rpms. After several attempts to stop, start, and proceed, I found the vehicle seem to be slipping when shifting from 2nd to 3rd gear, but would not go beyond 3rd gear causing the engine to strain and rev at an unsafe levels. Tried several times to shift to "l" to manually engage the engine, but it kept changing back to "d" automatic. Also noted that when the vehicle reaches the next programmed gear shift (e. G. 2nd gear to 3rd gear) it then jerks, stalls for about 2-3 seconds, then suddenly engages 3rd gear running at extremely high rpms and never shifts beyond that. Now check engine light is on. Vehicle has never been in an accident, damaged, or wrecked.