Hello @SaskiaRembrandt, thanks for asking. I do think it's important that people cite sources which is why I bang on about them a bit when I'm challenging people on aspects like the Christ/mystery cult comparisons.
One good place to start might be Bart Ehrman's fascinating book 'Did Jesus Exist?' Bart is an agnostic/atheist and an extremely well respected NT scholar, and argues fiercely against the Christ-myth proponents, along with the great majority of other scholars of the ancient world. I like to read him and others like him - Lindemann, Hoffman, Sanders - so that I don't end up in a Christian scholar echo chamber with nothing but confirmation bias for my own faith. Having read widely, I've really never come across any serious scholarship that gives the Christ-myth view any credence. In fact, the majority view is one of pouring scorn on the idea that Jesus did not exist.
There are around 40 different sources within the first 150 years of the events which recount the existence and the activities and death of Jesus Christ. These include the accepted NT writers, early historians and cultural commentators (Josephus and Tacitus mention Jesus and his life and death, Pliny the Younger, Lucian, Mara Bar Serapion, Suetonius, Thallus etc mention early Christian practices and the Christ figure whom they worship), early church writers (eg Clement of Rome, the Didache, Ignatius of Antioch, Polycarp), and later so called gospels which were not included in canon for a variety of reasons.
We accept the existence of some figures in antiquity with only one or two (non contemporary) sources, yet so many try to discount the sources around Jesus Christ when there are a startling number which mention a random preacher in an insignificant region. Enough to reconstruct his life and death at the hands of Pilate even without the gospel accounts, in fact.
I won't info drop a thousand details on this post, as that would just be tedious. But you might like to read this comprehensive article by an atheist scholar who discusses the evidence for the existence of Jesus:
armariummagnus.blogspot.com/2014/01/did-jesus-exist-jesus-myth-theory-again.html?m=1
I don't agree with all of his assertions, but what is interesting is how he comprehensively shatters the Christ-myth theories and provides the biblical and extra biblical evidence, outlining why it is useful evidence in terms of historicity.
If you'd like a list of further reading in terms of scholars, both skeptic and those of faith, I'm happy to provide that as well. It's fascinating stuff.