Born in Ukraine want to get ukrainian citizenship

Ukrainian does not allow dual citizenship.
As of now, you can apply for permanent residence after obtaining an immigration permit. At the same time you can get the immigration permit by proving you have Ukrainian heritage (Ukrainian ethnic origin).

The immigration permit is issued within one year after all documents have been submitted. Then you can apply for permanent residence that is issued within 7 days after applying. But first you need to prove your Ukrainian heritage and get a certificate of foreign Ukrainian that is issued within 90 days. So the full time schedule is about 15 months and one week. Ukrainian ethnic origin may be proved by relevant documents, testimonies of Ukrainians, foreign Ukrainians or organizations of foreign Ukrainians.