Thanks for helping out with translation work! This is the workflow for what you want to achieve:
If you do it this way and in this order, your work and customisations will not go lost in upgrades etc.
thank you
and how can I see directly where my translation will show to compare the Eng version and my translation? because sometimes we need to read the context to make a better translation.
What is possible to compare English with your langauge, you can find on https://docs.moodle.org/dev/Translation_FAQ#How_can_I_find_out_the_context_of_the_strings.3F and on https://docs.moodle.org/31/en/Language_FAQ#How_can_I_find_where_a_language_string_is_located.3F
You can't see your translation work show up immediately because it needs to be wrapped up in a language pack and installed on your site first. You can find the location of untranslated strings in the language pack by the technique described in my second link.
