DESISTIR is usually followed by a de. That’s because when you give up, you usually give up on/of something.
Você desistiu do apartamento? You gave up on the apartment?
Eu desisti da ideia. I gave up on the idea.
Não desista! Don't give up.
DEVER usually gets combined with another verb immediately following it to form powerful expressions.
dever + ser Ela deve sera apaixonada. She must be in love.
dever + ir Você deve ir. You should go.
dever + ter Deve ter sido amor. Must have been love.
dever + voltar Você deve voltar logo. You should return soon.
deveria Eu deveria ter ficado. I ought to have stayed.
ESQUECER is usually followed by a de. That’s because when you forget, you usually forget about/of something.
Esqueceu de mim? You forgot about me?
Esqueci desse restaurante. I forgot about this restaurant.
Ela esqueceu como dançar. She forgot how to dance.
Use estar to talk about temporary, passing things.
Eu estou atrasado. (I'm late.)
Onde você está? (Where are you?)
Estamos perto do metrô. (We're close to the subway.)
Eles estão no restaurante. (They're at the restaurant.)
EXPERIMENTAR & PROVAR both mean: to try out, to try on, to sample, to test
Experimentar has the additional meaning of: to experiment
Provar has the additional meaning of: to prove.
Eu vou provar esse vinho. (I'm going to sample this wine.)
Quer experimentar a caipirinha? (Do you want to try the caipirinha?)
Posso provar essas roupas? (Can I try on these clothes?)
Use these to talk about trying clothes on, sampling foods trying new things.
