…we can’t go days without our phones…
The structure to go + time + without sth is a useful way to talk about experiencing, surviving or enduring a period without something.
e.g. After our argument he went a whole week without speaking to me!
…you shouldn’t have put your phone in the water then…
The structure should/shouldn’t have done something is used to evaluate or criticise past actions or inactions.
If someone should have done something, then they didn’t do something, and you think this was a mistake. e.g. I had no idea you were allergic to cheese. You should have told me!
If they shouldn’t have done something, then they did something, and you think this was a mistake. e.g. You look exhausted. You shouldn’t have gone to bed so late last night.