the descendants of Adam
The information about where he came down from can be made explicit: "came down from heaven." This does not tell how he came down. Use a general word meaning "came down." (See: rc://en/ta/man/translate/figs-explicit)
"to observe" or "to look more closely"
one people with the same language
All the people were one big group and they all spoke the same language.
they are beginning to do this
Possible meanings are 1) "they have begun to do this," meaning that they have begun to build the tower but it is not finished, or 2) "this is just the first thing they have done," meaning that in future they will do greater things.
nothing that they intend to do will be impossible for them
This can be stated in positive form. AT: "anything they intend to do will be possible for them" (See: rc://en/ta/man/translate/figs-doublenegatives)
If your language has a way of urging or commanding people to begin work, like the English "Come on!" you might use it here. See how this is translated in Genesis 11:3.
let us go down
The word "us" is plural even though it refers to God. Some translate it as "let me go down" or "I will go down." If you do this, consider adding a footnote to say that the pronoun is plural. See the note on "Let us make" in Genesis 1:26. (See: rc://en/ta/man/translate/figs-pronouns)
confuse their language
This means that Yahweh would cause the people all over the earth to stop speaking the same language. AT: "mix up their language" (See: rc://en/ta/man/translate/figs-explicit)
so that they may not understand each other
This was the purpose of confusing their language. AT: "so that they will not be able to understand what each other is saying" (See: rc://en/ta/man/translate/figs-explicit)