Learn Turkish: Biz yorgunuz ama tembel değiliz. - We are tired but we are not lazy.

Just like the English word "but", ama sits exactly between the two ideas it connects. It doesn't change the word order at all. It just joins the first thought (yorgunuz) with the contrasting thought (tembel değiliz).

Why is the word for "we" (biz) only at the beginning? Don't we need to say it again after ama?

You don't need to repeat it! In Turkish, the personal suffixes at the end of words already tell us who the subject is. The -uz on yorgunuz and the -iz on değiliz both mean "we". The biz at the start is just there for a little extra emphasis.

Why does the "we are" suffix look like -uz on one word and -iz on another?

This is a great example of vowel harmony in action. The personal suffix for "we" changes its vowel to match the word it attaches to. Since the last vowel in yorgun is u, it takes -uz. The last vowel in değil is i, so it takes -iz.

Why do we use the separate word değiliz instead of a negative suffix?