"I will call you withing 2 hours" means that you will call anytime starting from this moment but no later than 2 hours after this moment. "I will call you in 2 hours" means that you will call no sooner than 2 hours after this moment. "The work will be ready in 2 hours".

"It's essential that everyone obeys the law" or "It's essential that everyone abides by the law"

"Can I make a call" is grammatically incorrect (but many americans use it anyway). If by saying "can i make a call" you mean to ask for permission to make a call (for example, you are at somebody's office, you need to make a call, but you don't have a cell phone. So you ask for permission to use office phone). "Shall I make a call" is used when you ask for instructions. (for example, your boss wants you to ask your co-worker to come to work right now. So you ask your boss whether you should call the co-worker right now or not")

Most oftern americans say "Great. thanks", "I really appreciate this", "Thank you very much".

"After my mother lays the table our cat likes to lie on it". It's obvious that the mother doesn't lie on the table, she just puts dishes on the table. But after that the cat jumps on the table and lies on it.