Sign languages are real languages, they are not pantomime or body language. Sign languages have syntactic rules and a lexicon of standardised signs.
Sign languages are not universal. Every country has its own sign language, and sometimes: more than one sign language.
Sign language is not the same as fingerspelling. Fingerspelling: every letter of a word is spelled, with specific handshapes for letters. Fingerspelling can be used for names and technical terms that the signer may not know the sign for. Fingerspelling is much slower than signing.
Sign languages use a different word-order (sign-order) than spoken languages. You can't use sign language and spoken language, simultaneously. Some people do speak and sign at the same time, but they are using 'Sign Supported Speech', sometimes called Signed English, Signed Dutch, etc. The spoken language is dominant, the speaker visually supports keywords in sentences, to support understanding.