Sé lá ar bith a chaithim i do theannta an lá is fearr liom.
Mar sin, seo an lá is nuaí is fearr liom.
This one seems awkward to me. I don’t think “a chaithim” is necessary and makes it cumbersome. “lá ar bith i do theannta” conveys the same meaning, it’s not necessary to say specifically that you’re spending the day. Someone may correct me there though. I would also say “is ansa liom” but that’s more a matter of taste.
Ná lig an traein gabháil thart gan stopadh.
Take that train. Don’t let it pass you by.
Tóg an traen sin/Téigh ar an traen sin. Ná lig dó gabháil tharat.
Ní ceannphointe é an sonas, ach modh taistil.
Ní ceann scríbe é an sonas, ach modh taistil.
These are all, of course, literal translations and there might be in some cases more idiomatic ways of saying these things.