For Academic Search Elite and other EBSCOhost databases, follow these instructions to change the language in which you are searching. When prompted, use your UNI Google account to log in. After you log in, under My Preferences, choose the arrow next to Select your language, as shown:
Another option
You can search in English but limit the search results (sources) to the languages you choose. Do so in the Advanced Search screen at the bottom by selecting the arrow under Language, as shown:
For OneSearch, currently the interface is only available in English.
You can search in English but limit the search results (sources) to those in languages you choose, under Refine My Results > Language as shown: