Interpreting multilevel mixed-effects linear regression

Hi,

I am doing medical research and I am currently facing some challenges.

I have received help from the biostatistics department and they helped me create this model:

mixed Concentration_of_1 bn.Randomization Dose_of_Drug_1 Concentration_of_Drug_2 Weight || ID:

Two groups were examined to see if Drug 3 had an influence on the Concentration of Drug 1. They were randomized into two groups, Group B receiving Drug 3 and Group A not receiving it.
Factors to also consider that might have an effect were Dosage of Drug 1, Concentration of drug 2 and weight. Each person had several samples.

I am having a hard time interpreting the coefficients. What do they really mean? And I was told that the p-values aren't of much importance here, but rather the confidence intervals.
And how come there is no coefficient for group B? Is this right?

Your help is much appreciated.
Array