can someone please confirm the following phrases are correct...i do not have turkish type so i relaise some letters may be incorrect

bence = i think

bence oyle = i think so

bence oyle degilim= i don´t think so

cocugun nasildir? how is your child?

cocuklarin nasil dir? how are your children?

oglunun nasildir? how is your son?

kizin nasildir? how is your daughter?

Turkce´de nasil soylenir? how do you say in turkish?   I have been told that you may use "soylebilirsin"

Bu adam sansli = this man is lucky

bence = i think in my opinion in my view

bence oyle = i think so

bence oyle degilim= i don´t think in my opinion / in my view I am not like that

Bence

Sence

Ona göre

Bizce

Sizce

Onlara göre

Note

Third person singular is Ona göre

so you don’t use ONCA cos it means  çok,  pek çok

Third person plural is Onlara göre

Onlarca means 25, 35, 80,.....

Lana

Thank you for your help.

Can you or anyone else help with the other sentences please?

çocuğun nasildir? nasıldır - vowel harmony rule - how is your child? You  can omit * dir  suffix cos its not used in colloquial speech

çocukların nasil dir? nasıldırlar how are your children? Iyidirler /Iyiler/ Iyi -they are well Here same You  can omit * dir  suffix also its possible to omit plural marker – ler/- lar cos the subject is already in plural çocuk-lar-in

oğlunun nasildir? nasıldır how is your son?

kızın nasildir? nasıldır how is your daughter

thank you Abla

Onlarca means 25, 35, 80,.....

Correct, but "onlarca" also means "according to them"

I only know what is written in my books

They are for beginner and maybe they (authors) wanted to escape from causing confusion for beginners 

ty for your explanation 

bence oyle degilim: i don´t think i am like that / i think i am not like that.

bence oyle degil: i don´t think it is like that / i think it is not like that.

bence: "in my humble opinion", ...