Keren, i think this can help you (unless you got everything explained ):
when you need to add a suffix that starts with T or D, it meens you need to add a dental suffixe. If the last letter before the dental suffixe is f/s/t/k/h/ç/ş/p , then D softens and turns into T, so you have a suffixe that starts with a T. If the last letter before the suffixe is a vowel or b/c/d/g/j/l/m/n/r/z (did i miss any consonants?), you simply add the suffix that starts with letter D. For example:
gitTim (i went)
korkTum (i was scared)
çıkTım (i went out)
yazDım (i wrote)
deDim (i said)
oturDum (i sat)
Your task would be to add dental suffixes to the chosen verbs (find some interesting verbs that would be useful to know (if possible)).
Best phrase to remember f/s/t/k/h/ç/ş/p is Çift Haseki Paşa remove the vowel sounds.