can two conj.(but and because ) be used together?
Solution 1:
Yes, you can put two conjunctions together, but only if the first one is a coordinating conjunction (and, or, so, but, for, yet, nor) and the second one a subordinating conjunction (because, after, although, since, etc.).
For example, but because and so although are correct, but not because but or although so.
As for the position of not, it comes before the subordinating conjunction it modifies. Consequently, your sentence is grammatical as it stands.