"Who will teach German?"
Translation:Vem ska undervisa i tyska?
There are several ways to say "teach" in Swedish. First, there is lära. So, if you want to use lära, the sentence will have two objects (the person who is learning and the thing that the person is learning). If the subject and the object (the person who is learning) are the same, you add sig (or mig, dig, etc.) because there still needs to be that first object. For example, Jag lär mig svenska (literally "I learn myself Swedish"). Mig is there to act as the first object. However, this construction (where the subject and who is learning are the same) means "to learn/study" instead of "to teach." Lära is used to mean "teach" when the subject is not the same as who is learning. For example, Hon lär dig svenska. (She teaches you Swedish). This is kind of confusing, so to sum it up, lära means "learn" when you are learning something from yourself, and "teach" when you are learning from someone else. If you have any questions about this, please ask me.
"Undervisa" works without an object, so you can simply say
She can also teach something
"Hon undervisar i tyska"
... and someone
"Hon undervisar oss i tyska"
"Lära" = teach doesn't work the same way. You have to tell what is taught
"Hon lär ut tyska"
... and if you add whom she teaches, you skip the particle "ut"
"Hon lär oss tyska"