Instead should we say " I work with an international law firm" . Please let me know which one sounds more right and natural. whether is it okay to use the first one. because i know its not grammatically wrong but is it natural.
"We" would say "We are working with an international law firm." just to be clear.
that said, the phrase "I am working with an international law firm" can have the subtle implication that you are only working with the law firm for a temporary period. Whereas "I work with an international law firm" has more of a permanent implication. It is up to you to determine which one is more fitting to your situation.