I'm sorry that I dont know what kind of motherboard is in the laptop, but I know generally the answer to your question. GPU's and CPU's are sodered directly to the board during manufacturing, so replacement/upgrading isn't possible. Someone who knows the motherboard might be able to confirm or correct me, but I'd bet on no. You do have the option of an external enclosure for a desktop type GPU, but they usually run 300-500. So for 300 for a low end enclosure, and 540ish for a GTX1070ti isn't worth it. Either find some amazing deals on enclosures and cards, or upgrade to a newer model.
There is no 1070 Ti for laptops, and no you can't change the video card unless you use an external one. This is why we recommend you get the fastest laptop you can afford, or even wait to get one and save some more money.