There is a rather distinct typ of speech in my village that is extremely similar to Icelandic, and I believe it is even considered a separate language.
So I guess I could say that I have some indirect skills in Icelandic, although nowhere near enough to read it fluently or anything.
One great way to learn another language, at least in the beginning, is to read relatively simple phrases as much as possible and learn the words that are used there by heart.
In fact I think this is the best way to learn new vocabulary, because it gives a clear context.
Also try to listen to French speech whenever you can (it might be a good idea to use French subtitles along with it until you feel comfortable with the speech itself, though).
And whenever you aren't 100% sure of why a sentence is written in a certain way, make sure to look it up and get a deeper understanding for the grammar structure before you continue.
And also, do not feel intimidated by the language.
It's very important that you have a confident attitude to anything you want to learn, and if you treat French as something that's simply something that you are ready to learn and that you have decided to become good at then it will become much easier.
You are the master of the language and of your motivation to learn it.
Depends on how you define "understand...".
Swedish, Norweigan and Danish are very similar in many ways (pretty much like Spanish and Italian, I guess) but I would say that spoken Danish is probably quite unintelligible, at least in Sweden.
Norweigan is super-easy to understand though, it's almost exactly like Swedish.
But then again, there's arguably a big difference between understanding a language and actually being able to speak it yourself.