hi,hope you are fine ,congratulation for your car and welcome back
you are doing good work for newbies
on commenting you are right read,understand others content and leave a meaningful comment there is just like respecting others
here are some tips to comment ,
follow the persons with high SP , check their posts and comments on it, try to make them friends,try to comment first if you can,comment when post are hot and do not have much comments,if you can't understand post you should avoid commenting on it,find the posts according to your interest