As Carole said, write down what symptoms you’ve had, when they started, how long specific things have lasted, whether any symptoms have hung about, or if things tend to eventually disappear.
Obviously s/he will have your previous notes and test results, but s/he will want to know from you what’s been the history behind the tests. Ie from your perspective, what originally took you to the GP, referred to the (useless) neurologist, sent for tests, etc.
Thankfully you’ve been referred to this MS specialist.
The questions you’ll need to ask are things that you think of between now and then. So start keeping notes of what occurs to you. I should think the primary one is ‘is it possible that I do in fact have MS?’ Or ‘what do you think are the chances that this will become MS?’ Or ‘what is the significance of the positive lumbar puncture?’ ‘And the negative MRI?’
And some things will be just part of the conversation you have with this new doctor. So will depend on what s/he says.
It’s a good thing your partner will be coming to the appointment. Partly so you don’t get flustered and forget half of what you wanted to say, and partly so between you, you’ll remember what is said!
Don’t worry about keeping on coming here and asking questions. We honestly don’t mind however many times you need to ask for help, just sound off or get some sympathy.