1.subjective=大家 verb=讨论 adj=好（Because group discussion is GOOD so I decide to discuss together) 2. subjective=商店 adj=便宜（Because the price is cheap so I might buy something in this shop ) 3. subjective=你 verb=去 adj=合适（it will be more suitable if you go there I think 还是doesn't has a specific meaning here,it is used to explain the reason. I don't know what I'm talking about,I hope it will help you.Please feel free to discuss with me.

Taking the examples you have 1. 还是大家在一起讨论好。 here, the adjective is 好, literally, "rather we should discuss together, it's good" 2. 看了好几家,还是这家商店的东西比较便宜。 here, the adjective is 便宜, literally, "rather (we should go to) this store, it's cheap" 3. 想了很久,还是你去最合适。 here, the adjective is 合适, literally, "rather you should go, it's appropriate" So this adjective indicates the reason why we should do something, following the word 还是. (why we should discuss together? why we should go to this store? why you should go? etc.) However, often we simply omit the adjective when the meaning is clear in the context For example, 想了很久,还是你去 is as common as the full sentence.

“还是” is an adv. and indicates "make a choice after comparing". For example, in your second sentence, "看了好几家,还是这家商店的东西比较便宜", comparing "好几家" and "这家商店", you come to conclusion that "还是这家商店的东西比较便宜。"

Hi Lusine ! According to those three sentences you've given , "还是"here means "still, nevertheless, however" 1. 还是大家在一起讨论好。 (after tried so many ways to do the job), "still"（还是), it's better to 大家在一起讨论. 2. 看了好几家,还是这家商店的东西比较便宜。(after seen so many stores), "still" (还是), 这家商店的东西比较便宜. 3. 想了很久,还是你去最合适。(after given mature consideration to all aspects of this problem), still, 你去最合适. Also, there are other uses of 还是. for example, 1.OR 是你"还是"我? you "or" me? 2.HAD BETTER 天色不早了，你还是早些歇息吧。 It' s getting late, you'd better go to bed now.

去掉“还是”完全不影响句子要表达的意思，“还是”只是表达一种语气，我不懂该怎么解释；不过初学者可以跳过这个词