Oh how sad

At 7 months it may be a bit harder to train, but maybe start small with treats. When you get his attention with a treat wave it over his head towards the back of him and after a while he will sit because he will be trying to follow it, makes sense? Reward him when he does sit, but occasionally with a pat or a 'good boy' in place of the treat.
As for the barking, that's a bit harder. Maybe try a spray bottle of water set to 'stream' and spray him with it every time he barks.

HTH


ETA: If it doesn't work out I agree with what LionsandBears suggested