Jobs for Biologist?

Maybe the market for biologists is not so good at the moment? And while your German might meet minimal requirements, being less than fluent will always put one at a disadvantage. Yes, there can be jobs in the sciences for English speakers but more likely for ones with a doctor title in areas of high academic or research.

Otherwise, one needs to really impress on job interviews; not just that they feel one is qualified but also a good match to the actual job and eventual co-workers. Appearing insecure, shy, overly arrogant or otherwise not making a good personal impression can be a determining factor that nobody here can judge with the information given.

Some people need coaching as they don't have experience presenting themselves well. I doubt there is a magic answer that anyone can give to say; oh, since you are a foreigner you just have to do x or y to succeed.