not bad 还行吧/还可以is a response to a question to a thing/person or something has already happened. net bad 可以 is a answer to a suggestion. -- 左一老师怎么样？ -- 还行吧。 A:How do you like Zoe? B:Not bad. -- 左一老师的课怎么样？ --还可以。 A: How do you like her classes? B:Not bad. -- 选左一老师的课怎么样？ --可以。 A:How about grabbing her class? B:Not bad.

Generally speaking, you are right in understanding the chinese characters "好的，还行吧 and 可以", such responses as these are denoting you agree to what he or she want you to do or agree his view of something.However, the extent of "agreeing" is different: "好的" means you 'quite' agree, "可以" 'just' agree , "还行吧" 'marginally' agree. For example, A : 您喜欢和我一起看电影吗? (Would you like to see a film with me?) B: 好的。 (Yes. I 'd like to) A: 你能把那本书借给我看吗? (Could you lend me that book (for me) to read?) B: 可以。 (Yes, I can) A: 如果我帮你捕获住那个小鸟，你愿意给我200美元吗? (Will/Would you give me $200 if I help you catch that bird?) B: 还行吧。 ( Ok, marginally agree) By the way, there are other ways to express agree with sb about sth , such as, 对(it is correct)， 行(right), 中(Ok), 没(有)问题 (No problem), 太好了(you are quite right) , these answers are especially used when you express ok to other's suggestion , request, or opinion. I hope it helps …

Yes, you are right. I would like to give you 2 examples. 1.If someone asks you for help and you are willing to help him or her, you can reply "好的"/“可以”/“没问题” 2. -你今天过的怎么样？ -还行吧。(a little bit sad) PS The use of these words depend on different contexts or people's intonation, so it's difficult to say😆

Yes, I think your usage is correct. And sometimes 还行吧 also means just so so, when other people ask your life or situation. 好的 and 可以 are similar when you use them to response to a command.