Hello
I plugged my electric guitar directly into my focusrite audio interface and the signal I get is really low.
Does anyone know how I reach a decent output level?
And Into which of the many inputs of which of those many focusrite interfaces… 
Turn up the output volume…, turn up the input gain…, both…, use a DI box…, turn up output volume… - depends on the answers on Q 1.
Until then start reading your interface´s manual, it usually tells you, if and where to plug a guitar to get best results…