How to Navigate within Category? Lot of codes here on stackexchange didn’t work

Both previous_post_link and next_post_link accept a 3rd boolean parameter $in_same_term, which specifies whether link should be in a same taxonomy term.

So in your scenario you would be looking to make the following update:

previous_post_link

<?php previous_post_link('%link', '&Lang; &Lang; &Lang; %title') ?>

updated to

<?php previous_post_link('%link', '&Lang; &Lang; &Lang; %title', true) ?>

and next_post_link

<?php next_post_link('%link', '%title &Rang; &Rang; &Rang;') ?>

updated to

<?php next_post_link('%link', '%title &Rang; &Rang; &Rang;', true) ?>

error code: 523