Deafblind people communicate in many different ways determined by the nature of their condition, the age of onset, and what resources are available to them. For example, someone who grew up deaf and experienced vision loss later in life is likely to use a sign language (in a visually modified or tactile form).
To burn someone's bridges is too forget about them. Ryan built bridges, meaning he still might want to come back to her. He is telling her to burn them, because he can't seem to do it himself. It isn't easy for him to forget her, and hes asking for her help.
burn up. v. 1. To destroy something or someone by fire or heat: She burned the contract up. He burned up all the photographs. 2. To be completely destroyed by fire or heat: The cabin burned up, leaving only ashes. 3. To expend something; use something up: When I was on vacation, I burned up all my money quickly.