How to train adult rescue dog

I recently adopted a 2 year old chihuahua dachshaund cross. He is an amazing addition to the family and has become very attached to me and is also getting along with our 5 month old black lab. My concerns are that whenever myself or boyfriend try to pick him up he pee's. He bends down in a fetal position and urinates. He was with a family for almost a year and they returned him to the shelter. I am not sure if he was abused and now has a fear of being approached. This only happens sometimes, I always approach him calmly and pet him before I pick him up. This has greatly helped. The volunteer at the shelter had told me about this issue before I adopted him so it has been going on for a while so is it possible to fix? Also he is not potty trained. I take him outside both alone and with my other dog but he does not seem to catch on. He will normally go to the washroom during walks but he isn't improving when it comes to going to the backyard. Other than continusously taking him outside is there anything else I can do ?

It sounds like you are doing what you need to do in the potty training area. Hopefully he will soon catch on.

I think youalso need to work on building his confidence. Google confidence building exercises for dogs. That should give you plenty of ideas.

hmm just continue to train your dog. I also have a dog with same problem, after three months of training, my dog knows now how to pee properly.

That's great but it is very long time. If you took assistance of dog training centres or dog daycare then could be one month and your dog would be trained in lots of things.