Media storage can consume quite a bit of space. To move it to S3 or S3 compatible provider, edit /app/data/env.production using the File manager and add something like this:

S3_ENABLED=true
S3_BUCKET=bucket-name
AWS_ACCESS_KEY_ID=<key_id>
AWS_SECRET_ACCESS_KEY=<secret_key>
S3_REGION=<region>
S3_PROTOCOL=https
S3_HOSTNAME=<hostname>

See this thread for more information.