Tell me please If it is possible to use "the" before "two" in some situations. For example, I am at a shop and I ask the salesman to show me the best suits he has. So he gets me one suit and then another and I say "I will buy the two."
Yes, the can come before numbers like in your sentence, but if the subject is not introduced, you will need to include more information:
We have your shoes in two other colours: red and black. Which do you want?
I'll buy the two [pairs of shoes].
As mentioned in the comments, in English there are different phrasings of your sentence that are more common, if that is what you prefer:
I'll buy the two of them.
I'll buy them both.
I'll buy both of them.