What I would suggest is to step out of the shower, get dress and put a towel or a bath robe over your shoulders. Grab a spray bottle and your conditioner and apply a lot of it to the tangled mess and slowly work it out, hair strand by hair strand from the bottom. This can be fixed, it just takes time and patience and a lot of conditioner.
(I've detangled 4 cm mini-dreads after wearing extensions that grew out a bit too far. Took A LONG TIME but it can be done. Just take it slow)