We use "should" to give advice or state that something is a good idea in the present or future tense. We use "should have" to refer to past actions that someone did not take but would have been better if they had, such as telling the truth, not smoking, consulting a doctor, or taking an umbrella in case of rain. "Should have" expresses regret or disappointment about past decisions or missed opportunities.

2. should vs. should have
We use should for the present and the future to
give advice to someone and to say that
something is a good idea. (следует/не следует)
o You should tell them the truth.
o You shouldn't smoke, it's bad for you.
o I don't think you should do it.
o You should consult a doctor.
o You should take your umbrella. It might rain.

3. should vs. should have
We use should have for the past to say that
someone didn't do something but it would have
been better to do or not to do it. (следовало/не
следовало)
o You should have told them the truth.
o I shouldn't have shouted at you. I apologise.
o I should have given up smoking years ago.
o I should have studied more for my test.