In order to set up Magento 2 Auto Language Switcher Module please go to Stores > Configuration > Magefan Extensions > Auto Language Switcher.

Magento 2 Auto LanguageSwitcher,General,ExtentionRestrictions,Default storeViewBy Country

General

 Make sure if the extension is enabled choosing Yes in the Enable Extention select box.

Magento 2 Auto Language Switcher Genral,Enable Extension

Extension Restrictions

In User Agents you can set the user agents (bots) this module will be disabled for. E.g.: for Google bot, this module will be disabled, it will crawl the site as usual.

Magento 2 Auto Language Switcher,Extention Restrictions

Default Store View By Country

In this section, you can configure language switcher by country.

Magento 2Auto Language Switcher,Default Store View ByCountry

Select a region and country you are interested in and set default store-view for it. You can leave default settings to detect store-view based on customer browser language.

Magento 2 Auto Language Switcher ,Default Store View BY Country

Once all of the configurations have been finished don't forget to press the Save Config button and Flush Magento Cache.

Magento 2 Save Configuration