grammar - usage of 『は』and『が』with adjectives { na-adj and i-adj }

i really had this question in my mind and it caused me a lot of pain. My question is : what is the difference between using ( wa ) and ( ga ) with adjectives ? i got confusion because i studied that japanese doesn't have real adjectives , instead it has adjectival verbs ( i-adj ) and adjectival nouns ( na-adj ) and both of them are verbs that modify nouns as it is . and it was mixed up with what i have studied about ( wa ) and ( ga ) , that in the adjective-predicate sentences we should use wa usually . can any one here solve my confusion please . thank you in advance . signature : passionate of japanese