To whom it may concern: I have developed a multi-lang site, all necessary measures are taken in regard with plugins, menuitems and its associations, modules etc. The module change language works perfect, yet when I login in French language, I will be redirected to English part and this is while I already fixed redirect files in both French and English mods, the same with login menuitems, also French and English login mods appear only on French and English pages. What could be the problem? Joomla version is 3.8.1 Kian William

I have developed a multi-language site, all necessary steps are taken in regard with plugins, menuitems and its associations, modules etc. 
The language-switcher module works perfectly, but yet, when I login in French language, I am redirected to English part and this is while I already fixed redirect files in both French and English mods.
The same with login menuitems, also French and English login mods appear only on French and English pages.

What could be the problem? 
_{Joomla version is 3.8.1}