People trying to learn german are such fucking troopers.
German has terrible grammar
Verbs ending in -ieren are conjugated in participle II without a leading ge-. Examples for "schneiden" and "rasieren":
Ich habe mich gestern schnitten. ❌
Ich habe mich gestern geschnitten. ✅
Ich habe mich gestern rasiert. ✅
Ich habe mich gestern gerasiert. ❌
Most germans don't even know german grammar and are just doing it (mostly) correctly from intuition.