Last week my menstruation was finished, now I received another one. It obvious that is not menstruation. Many I pray and fast, or not?

Praise be to Allah, the Lord of the World; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The preponderant opinion is that there is no minimum or maximum time limit for the menstrual period. Therefore, if the blood that came to you after the end of the menstrual period is of the features of the menstrual blood such as black, thick and bad - smelling then it is considered menstrual blood and all the rules of menses apply on it. If it does not consist of the features of menses then it is not menses but it is Istihadah (prolonged flow of blood) and then the rules of menses do not apply to it.
Allah knows best.