Verified answer

I understand what you are telling me but I can't speak.

I understand what you are speaking about but I can't speak.

I understand what you are talking about but I can't speak.

I understand what you are saying but I can't speak.

tell - говорить (рассказывать)

say - сказать (что-то)

speak - говорить (разговаривать, выступать)

talk - говорить (разговаривать)