What are some ways to communicate easier

I can basically never talk to anyone except my twin sister who also has selective mutism, I use the search thing on my phone to talk back and forth with her, anyway I can’t even use communication cards, I can’t let anyone hear or see my words, it’s so annoying, I know there’s basically no way to talk if I can’t share what I have to say, the only person I can sometimes talk to is my mum, I can always talk to my twin sister as I said, it’s mostly asking for things that’s hard I can mostly talk about other things, I’m thinking that when I need to ask for something I could just say “I kinda want McDonald’s” or something like that, maybe wording it differently could help me. I’m basically answering my own question here, tell me if there’s any other way I could talk or just let my mum know what I need/want. Also sorry for the random added thing but last time I posted something like this someone got my words wrong and just said “you’re talking right now” I mean I can’t let anyone hear or see my words in person, like I can text my mum when she’s in the other room but not when she can answer me with words and i can see her reaction