docker – how to change UID of user in image/pod

I launched Retool software in Openshift.

I have error in pod:

“user running container is not the expected user, retool_user (uid 1001) in retool_user_group (gid 1001)”. Pod has different UID 1001260000.

As I understood Retool requires user – retool_user & group – retool_user_group.

I changed UID & GID in Dockerfile with commands

RUN groupmod -g 1001260000 retool_user_group
RUN usermod -u 1001260000 retool_user 

But I received image with size over 300 GB. How to rebuild image with lower size or solve problem with UID of retool_user? My Dockerfile:

FROM tryretool/code-executor-service:latest
RUN groupmod -g 1001260000 retool_user_group
RUN usermod -u 1001260000 retool_user 

Question is updated.