Opening the url with the language of the previously opened community's language

There is a way to pass the language via query string, but I believe it requires some configuration for your community first. Please file a case via our case portal so that our Support team can work with you to get that configured.

After it's been enabled, see the first option on this page for more details:

http://lithosphere.lithium.com/t5/support-knowledge-base/Viewing-the-community-in-another-language/ta-p/69088