I recently started with duoLingo, mainly to brush up my Swedish. However, I found that I like it so much, I started Danish and Irish as well (and will defenitely start Norwegian when it comes up!). However, I would be VERY interested in doing a Finnish course.. It's such an interesting language I think. I have no idea if you can do requests like these, but I thought I'd give it a try.
Do you speak Finnish? If so, apply to the Incubator please! I desperately want to learn Finnish. :) Unfortunately, even though many of the languages are developed by volunteer effort, it still takes a lot of work to get a new language on Duolingo, so I think it may be awhile. :_(
The similarities exist mainly in grammar and syntax, the similarities in words are few (even when they have a common origin, they are often morphed to unrecognizable...) But the logic how language functions is probably easier for Hungarians than for, say, English.
For words the Swedish course is probably the most helpful, a number of common loan words are actually recognizable (at least after one learns how Finnish usually morphs the loan words...)
I suspect part of the reason Finnish has not gone forward is that Duolingo system is not built for agglutinating languages using lots of suffixes and they are still ironing out how those should be dealt with in Turkish and Hungarian courses (currently in incubator). It would probably be necessary to see those courses released and maybe get a bit of user experiences in beta to help build a better course.
The thing is, it's pretty much impossible to mix up Finnish with anything. Unless you are learning Estonian.
Having said that, I do have moments when I can't think of the right word in Italian, yet mysteriously the Finnish word pops into my brain instead, as if that would help. ;)
:) yeah I think Finnish and Italian are different enough. OP is doing Swedish and Danish, but thankfully they already know Swedish previously. I got pretty tripped up with Dutch during German. With Swedish I get that vocab mixup you're talking about :/. But mostly one helps me remember the other. I'll see the Swedish word and know it's very similar to the German word. Sometimes I can't put my finger on what the German word is, and it makes me feel like I should learn my vocabulary better in German - probably because I should. (An example by the way is "to lose" = "förlara" = "verlieren"... they sound closer than they look). Also, I didn't realize Estonian was in any way related to Finnish.
I certainly wouldn't recommend that anyone starts with two similar languages at the same time although, like anything, I have seen some people on the forum getting on okay with it. I generally suggest people try to get at least an intermediate level before taking on an extra language. Some people are smarter than me though, and manage two from the start.
Finnish is quite closely related to Estonian, and very distantly to Hungarian. Those are the only languages it has any connection to, hence the reason it sounds so fascinatingly different to anything else. :)