Should I use "let's" or not?

1 and 3 sound ok to me! But I usually use "If someone wants to know more, please feel free to contact me.". Anyway, with your example, I think you should use "let's" in speaking. It sounds friendly. But "let's" doesnot sound formal!

Hi Ruslana,

"Let's" is a contraction for "let us". Hence, sentence (1) will not make sense if the contraction (let's) is used. The version-- as suggested by TammyBaby--will work fine.

Tammy
Thank you for the explanation!

Rishonly
Sorry but I don't speak English as well as I would like to. That's why I quite do not understand the phrase: "...sentence (1) will not make sense if the contraction (let's) is used". Would you mind saying it one more time but with other words, if it is possible?..
I do not understand if you mean that sentence (1) is correct. Tamm

Hello Ruslana.

1. If someone wants to know more, let's contact me.
2. If someone wants to know more, let contact me.
3. If someone wants to know more, contact me.

In your examples, both sentence #1 and sentence #2 are incorrect, at least in my understanding.

The verb 'let' has varieties of meanings. Here, "let" has been used as an auxiliary in imperative form

Yes, you did. Many thanks! :-)

Great! Thanks.

Tammy
Do you speak American or British English?

I speak British English, Ruslana! But sometimes, I use some words from AmE., for example: color or candy, etc. British English is more difficult to learn because it has a lot of rules while AmE is rather open. But I think it's better to learn the harder.

Hi TammyBaby,

Thanks for your feedback. The imperative form has several functions:expresses a command, makes a request ,gives a direction, suggests someone to do something.As you see, 'suggestion' is one of the functions of 'imperative mood'.

Tammy
I am learning British English, too. Perhaps I do not know AmE very well but I think BrE is much more understandable. :-)