If you are having a difficult time learning german because your previous exposure to french is getting in the way, this is called

The answer is "proactive interference".

When there is an interaction between the material you newly learned and the past behavior, material you learned in the past that causes disturbance in recovery of memories, this is referred to an interference. On the basis of that disturbance, interference is divided into two types or categories that are: Proactive Interference

Retroactive Interference