The difference between "böyle" and "öyle"
The first difference between them is "near" and "far"
Böyle is used for near activities
Öyle is used for far - away activitie
Example: You see your friend opposite (a bit far 4-5 metres) you who tries to repair his computer, and you understand that repairing way is not true. So you can say to him as "Öyle olmaz!" (means, you can't repair it like that way)
You are with your friend, near you, you are together, and he tries to repair his computer, may be also you are looking his rearing way and understand that repearing way is not true: So you can say to him as "Böyle olmaz!" (means, you can't repair it like that way)
The second difference between them is "now" and "past"
Böyle is used for "present continious, today, at that our, at that moment..."
Öyle is used for "past...yesterday, last year, last century..."
Example: You had a busy day and that night you say your friend that "I didn't expect such a busy day, but I had." Böyle yoğun bir gün yaşamayı beklemiyordum.
You had a busy yesterday and you say your friend about yesterday that "I didn't expect such a busy day, but I had." Öyle yoğun bir gün yaşamayı beklemiyordum ama yaşadım.
The third difference between them is "tangible" and "intangible"
Böyle is used for "tangible" situations
Öyle is used for "intangible" situations
Example: You meet your girl friend with your mom and you say your mom "Have you ever seen such a beauty girl mom?" Daha önce böyle güzel bir kız gördün mü anne?
You talked about your mom whom you saw a girl you met at that day and yu couldn't forget, and you laud her beauty to your mom "Mom! It's a lovely girl that I can't describe her beauty" Anne! Öylesine güzel bir kızdı ki anlatamam.
But please don't forget!
Sometimes there are exceptionals situations...