Hello, How have you been? Here you have the explanation of "dever" and "ter": https://ciberduvidas.iscte-iul.pt/consultorio/perguntas/dever-e-ter-de-em-normas-oficiais/26868

Hey Cristiana! Actually These words have the same characteristics that the same words in English. It depends on the context and the emphasis you want to express. The example you gave is right, you could say: "Você deve virar à direita." or "Você tem que virar à direita." The difference is that "Deve" is more strong. For example: You should turn right. - Você tem que virar à direita. (it's an advice. You should do this if you want to go to the stadium, for exemple.) You must turn right. - Você DEVE virar à direita. ( It's an obligation. You have to do this.) It's a little difficult but we use in the same way that in English. "Deve" can be used for 'logical conclusions' just like 'must' in English. Exemple: She walked 5km. She must be tired - Ela caminhou 5km. Ela deve estar cansada. In this case you can't use 'tem que estar cansada". It doesn't make sense. I hope it helps you!

thank you to everybody! Muito obrigada a todo o mundo! Now it's clear!

Hey Cristiana, the difference is really simple. The word "dever" you MUST use when you are saying that something is mandatory. Ex: Você deve lavar a louça! Now, the word "ter" is referring to an advice Ex: Você tem que fazer suas tarefas de casa. I hope you understood it now :)

Eu acho que "ter" = obrigação, e "dever" sentido de dúvida.