1) When do I use 'Öyle'. 'Böyle' and 'işte' ?
Böyle and Öyle come from the demonstrative pronouns Bu/This and Şu/That
Böyle: like this, this way
as an adjective
Böyle bir ev daha önce hiç görmedim.
I've never seen 'a house like this'/'such a house' before.
as an adverb
Bana böyle bakma.
Don' look at me like this.
Şöyle: like that, that way
Şöyle bir araba almak istiyorum.
I want to buy a car like that.
Şöyle yürürsen düşmezsin.
If you walk like that, you do not fall.
Şöyle has a third use.
But the meaning does not change if you sjip and don't say it, just a colloquial term.
(Şöyle) bir uyuyayım dedim, kapı zili çaldı.
I just felt like sleep, the doorbell ringed.
Şöyle bir yürüyelim (or just Yürüyelim mi / Haydi yürüyelim), belki alışveriş de yaparız.
Let's have a walk, maybe we can do shopping, too.
işte: right here, here it is ----- you point at a place
-Where is my key? Anahtarım nerede?
--Right here, it is. İşte burada.
When you use the word işte; it is like pointing the place in this sentence. Actually if you take it away, the sentence means the same in any case except;
iş: job, work
işte: at work
2) What does 'Saçmalama means ?
Don't be ridiculous : Saçmalama
3) Why is "Benim" used instead of "Ben" sometimes ?
Benim is the genitive form of the word Ben
Bu benim. This is mine. / This is me
Bu benim arabam. This is my car.
4) Why is also "bana used instead of Beni"
I understand the difference between accusative and dative, but sometimes i get confused
For example; (Sana ihtiyacim var ) why not "seni" what's the difference and how can i figure it out ?
It is the best and I think the only way to learn which case a verb requires when learning what it means.