Recently I came across and article that suggested that much of Norse belief was made up by Christians in the 12/1300s e.g Ragnarök along with much of Norse lore. If this is so what did they actually practice/ believe in?
We don't know, as there aren't any written records of worship from first-party sources. The archaeological record suggests bear-worship in some parts, lots of animal sacrifice, the use of tiny gold fillets as possible veneration objects, rune-charms, etc., but we have no real context for all of their use.
We know that Þórr, Týr, Ullr, Baldr, Óðinn, and Frigga/Freyja were worshipped from things like place-names and the Merseberg charms (which are 10th century and copied by a Latinate monk in Fulda, so are probably our most reliable sources for magic and myth from the era in question)
A good bit of research has gone into this, and I would highly recommend you take a look at Stefan Brink and Neil Price's The Viking World, Price's The Viking Mind, and Terry Gunnel's entire corpus of work on ritual and performance.