Quick Start Manual Translations - Please help

[multi.flexi]

@Luke  I finished Czech translation.
Few typographical (nazi) remarks (not only) for English:

1. SI units (including bytes) should have space between the number and unit and thin space (U+2009) between groups of three numerals (may not apply for numbers consisting of only four digits before or after decimal point).
   
2. Use × (U+00D7) instead of x for multiplication.
   
3. Use ″ (U+2033, double prime) instead of ” for inches.
   
4. I think it would be better if there was a repository on GitLab with e. g. LaTeX documents, including images which could be also translated. Something like LaTeX is better than WYSIWYG. I am up for the task of managing the repo if you want. It would be great opportunity to learn more.