Completing a novel, especially a large one, is more about mental preparation and discipline than skill.
If you're set on writing your novel in English, then find a friend that has a strong grasp in the English language or find a native English speaker online that is willing to read and edit your work. This person could essentially double as your 'cheerleader', a person you go to to help you stay motivated and to bounce ideas off of.
I find the most ruthless part of writing is the isolation, so try to surround yourself with other writers or creative-types that are passionate about their work. If you can't find friends or a writing group in your area then you can join online forums. Events like Nanowrimo (and its spring/summer version, Camp Nanowrimo are great opportunities to connect with other passionate writers that are in the same position as you are.
Make sure that you set aside a consistent period of time for your writing. If you're disciplined and you always write at a particular time and/or on a particular day then you're making it just a little easier for yourself because you're mentally preparing yourself for writing. That time doesn't have to be spent just writing either. If you haven't already, you should spend time researching the topics necessary to make your characters, plot, and setting plausible.
Preparation is a significant aide when doing long-term projects. So, I recommend you write an outline with all of the major points you would like to hit. Whenever you sit down to write, look at this outline and pick the points in your story that you would like to work out that day. Using your outline as a sort of to-do list helps to turn your project into a list of much smaller, easy-to-complete tasks. Just don't allow your preparation to become a way to procrastinate.
Lastly, I think it's important to remember that your first draft is for you. You don't need to show anyone your first draft if you don't want to and you probably shouldn't. Don't jump in expecting your first draft to be a work of art. Allow it to be messy. Use bullet points. Leave entire sections as poorly punctuated notes. It doesn't matter, just as long as your first draft contains everything you need to craft the final product. So, even if you feel you aren't prepared, just write! Dump everything you're thinking about the story onto paper (be it real or digital) instead of keeping it as a glorious image in your mind. This will allow you to see what you really have and it will eliminate the dreaded blank page.