ozgurs Hello
You can create a new module position and load this position to the main nav block of template. Try following this tweak:
1/ Create a new module position: called lang for example
<position>lang</position>
2/ Go to Backend >> edit template style of JA Vega >> Layout settings >> edit mainnav block:
and add this line of PHP code as screenshot:
<jdoc:include type="modules" name="lang" style="raw" />
3/ Go to Modules >> assign Language Switcher module to this lang position.
It will show next to the main menu.
