I’ve only been able to answer your questions these days.
If the code is garbled, change the encoding:

" 默认编码 {{{
if has('vim_starting')
    if &encoding !=? 'utf-8'
        let &termencoding = &encoding
    endif
    set encoding=utf-8
    set fileencoding=utf-8
    set fileencodings=ucs-bom,utf-8,default,cp936
endif
" }}} end

It is recommended that you first learn the complete vim configuration on github before starting the configuration. It may be better to play around with those good configurations than to work hard, and if you encounter problems with their configurations and raise an issue, most of them will be happy to respond. Or you can just take a look at it. It won’t take a long time, but it is very useful. You can often see the pitfalls that others have stepped on and avoid detours. Imitation is a good way to learn.

This problem is mostly due to encoding or fonts. Since I don’t use GVIM very much and I don’t use it under Windows, I can only give this suggestion.