I'm falling through the map and can't open anything with the "E" key. What can I do?

Please go to the settings and enable the "Network Workaround" option. If this is not successful: Are you possibly using 1&1 as your internet service provider? In that case, I recommend calling their customer support and requesting the deactivation of DS-Lite. Be persistent and don't let them brush you off - usually, this step is performed without any issues.