In this sentence:
簡単なレッスンを選びましょう
What is the meaning of ましょう ？
I’ve always been told it means “Let’s” yet the translation doesn’t use the word “Let’s” at all.
It’s basically “let’s”. See this grammar lesson: Nihongo o Narau - Lesson 11.
What does the translation say?
To MrsPirate
You know the difference between the one with ”Let’s" and the one without ”Let’s”.
Actually, there is not a big difference in this context.
The standard sentences in the lesson you mentioned are as follows;
Let’s choose a lesson that is easy for you.
Let’s choose a lesson that is interesting for you.
It is possible to translate the following sentences literally into Japanese. But It’s something like a tone of command. You’d better not learn the sentences when you are a complete beginner.
Choose a lesson that is easy for you.
簡単な レッスン を 選びなさい。
Choose a lesson that is interesting for you.
興味 の ある レッスン を 選びなさい 。
@MrsPirate - As skyblueteapot and Shigeharu have already pointed out, ましょう does translate roughly to “Let’s”. Personally, I find it a little easier to understand if I translate it more generally as an invitation or request.
For example, when I see 「簡単なレッスンを選びましょう」, the actual translation depends on context. If the speaker was going to study the lesson with me, I would think of it as translating to, “Let’s pick an easy lesson”. But if the speaker wasn’t going to study the lesson with me, I might think of it as, “You should pick an easy lesson”.