I want change the HDMI output resolution

Hello … I have a Banana Pi M2 Berry and I want change the HADMI output resolution. I have read the section “the final solution of compulsive modification of HDMI output resolution” in this Forum and I’ve tried doing this in the uEnv.txt file, but I have not had any success. Can someone please explain to me how I must make changes in this file in order to change the resolution? best regards Jurgen

sudo bpi-bootsel BPI_M2U_1080P.img.gz