The Upanishads and all talk about knowing God, but they stress that You can never know God by reading or knowledge, but only through Meditation. Religions on the other hand had been propagating speudo-Gods through bibles and other texts and causing hatred and egoistic tendencies knowingly in populations. If they find parallels from Gita and sanatana Dharma in Bible, then Bible, which had come at a latter stage is certainly a plagiarist work intended to transfer the knowledge of the Ancient land to the ignorant of the West.
If you wanted really to find God, then forget about Gita or Bible and Meditate on the Heart with the thought of the Omni-Pervasive-Infinite, accepting him as your teacher, Guru and Guide. Then see the results for yourself after 1 year of such practice daily twice for 1 hr, early morning and evening. He does not have to have a form or name, But for simplicity, you can take him as light in your heart. Remember, light can only be seen only when it reflects on something, but even in darkness, there is light.
Religion is only a Humbug, and Islam and Christianity are more so, as they make people accept only their ideologies as God, and others as false.
I wonder What God was before these religions, and How people survived with the false God(s) before them(according to them). But certainly, world was more peaceful before these religions have come. And they have been originated almost at about the same time and almost at same place.