Can you communicate using sign language?

I can only do a limited number of signs, days, months, bath, coffee, milk, sugar, apple, box, bag and other similar stuff.

I wish ! This is one of my biggest goals

Yes.

I can sign the basic pleasantries including a few offensive words. Other than this, I am useless in sign language.

Yes - I use BSL regularly as I have a good friend who communicates with it 🙂

Nah, I'm horrible. It'd be a disaster if I ever turned deaf or mute

A little bit but I’d like to be better

Not very much. I was working briefly in an office that served customers with all types of specials needs and learned how to take tty calls. One of the clerks could sign and taught me a few commands so I could assist customers who came down in person.
My brother took classes and was actually very proficient. He occasionally gets to help people with it, as he did when he was a policeman.

Afraid not.