Praise be to Allaah.
This is a great effort that you have undertaken, and you are to be congratulated for the results of your research and your questioning of the Muslim girls.
What you need to know are the basic matters which are easy to learn, such as the meaning of the Shahaadatayn (the two statements of faith) - which are the key to Islam - and the six pillars of faith (eemaan) and the five pillars of Islam. You should also learn how to pray so that you can begin to pray after you pronounce the Shahaadatayn. You can find a lot of information on these matters on this website, in the section on 'aqeedah (correct belief), under the headings "Issues relevant to accepting and embracing Islam" and "Basic tenets of Islam for non-Muslims."
As regards your mother, we hope that she will not try to stop you becoming a Muslim. Treat her with kindness and tell her about Islam in beautiful words - maybe she will embrace Islam too. If you are afraid that she may turn against you if she knows about your Islam, then you do not have to tell her about it. Embrace Islam in secret, and do as much as you can of your duties towards Allaah. Allaah will never forsake you; in fact, He will help you and support you, if you turn to Him. We ask Allaah to help you follow the truth and adhere to it. We are prepared to offer any help that we can. Peace be upon those who follow true guidance.
And Allaah knows best.