I am back哩句個back不用加-ing?

因為這句的back不是動詞，是個ADVERB，形容一個狀態
就如同I AM DONE一樣

Hi, cos' "back" is not a verb in this sentence. In this sentence "I" is noun, "am" is verb.
so ... just "I am back" is ok.
for ur another examples, "make" and "do" is a verb, so you have to write as ... "I am making" and "I am doing".

Back is adverb hear, not a verb.
You can't say "I am do."But you can say "I am done."
Hear"done" is a verb but this kind of sentences are called "the passive voice".For example "It is called apple." We use the passive voice because the apple will not call itself.

back here is an adverb.