One of the ways to use 还是 (háishì) is to have it mean "you had better," similar to how in English we may say "I think you had better start on your homework."

Structure

还是 as an adverb can express "had better" or "it would be better to". The idea is that the speaker has given the matter some thought, and after considering it, has finally come to a decision. The announcement of this decision will frequently include 还是, and it usually comes before a verb or a subject.
Subject + 还是 + Action + (吧)


吧 is often placed after this structure, as it's a suggestion.
Examples

nǐ bú huì， háishì wǒ zuò bɑ。
你 不 会， 还是 我 做 吧。
You don't know how; I had better do it.

Wǒ è le, wǒmen háishì xiān chīfàn bɑ.
我 饿 了，我们 还是 先 吃饭 吧。
I'm hungry; we had better eat first.

Zhèlǐ tài zānɡ le, wǒmen háishì zǒu bɑ.
这里 太 脏 了， 我们 还是 走 吧。
It's too dirty here; we'd better leave.

Nǐ háishì xiànzài jiù ɡēn wǒ shuō bɑ.
你 还是 现在 就 跟 我 说 吧。
You'd better talk with me now.

Nǐ bìnɡ le zhème chánɡ shíjiān, háishì qù yīyuàn bɑ.
你 病 了 这么 长 时间，还是 去 医院 吧。
You've been sick for such a long time. You'd better go to the doctor.