i need a pencil. —>Bir kaleme ihtiyacım var .
Do you remember the word “var”. If not please look at the previous lessons. var means there is also can be used as i have.
the word ihtiyaç means need so ihtiyacım var means i have a need. So the correct translation will be something like i have a need to a pencil.
Eğlenmeye ihtiyacım var . : i need to have fun.
Koşmaya ihtiyacım var çünkü çok şişmanladım. (Try to figure it out by yourself) you can ask from the comments as well.
So you can create sentences with your needs. to the comments page again. so i can correct you.