Don't forget about the now no longer extant Manx spoken on the Isle of Man:-)
It is still spoken Lyzko :) There is a primary school on the Isle of Mann where everything is taught through the Manx language. It's very similar to Irish, perhaps even more so than Scots Gallic. Both Gallic and Manx are derived from Irish. A Manx speaker and an Irish speaker could converse and understand each other but Manx is more like the dialect of Donegal Irish so if you spoke Kerry Irish you'd have to concentrate hard listening to a Manx speaker.
Irish (where the spelling is akin to a natural disaster...
It's really quite easy once you get the hang of it. Once you get used to looking at it and read enough of it, it becomes automatic and you really don't have to think about it anymore. Interestingly, in Irish we have no formal mode of address, but in Scots Gallic they do, similar to French and German where they use the second person plural for formal address. In Irish and Scots, that's 'sibh' pronounced 'shiv'. The Scots use it like the German 'Sie' or French 'vous', but we don't have any of that kind of nonsense in Irish :))
What about Welsh,Cornish and Breton?
Not related in any way to Irish.