Questions about pug exercise and training

Hello everyone — first time poster here!

I have a silly squishfaced pug and recently started training him with a professional trainer. I take my fellow out for two walks a day of about 20 minutes each, one in the morning, one in the evening. The trainer said that this is too much for a pug — that actually, some days, they needn’t be walked at all, provided they’re properly potty trained. She said this is because in the long term it’s bad for their legs. How often do you guys exercise your pugs?

Also, has anyone else found housebreaking a pug to be a total nightmare? I’ve been trying for four months now and Lord Nibbler still has ‘accidents’ every now and then…