Hi LexiconLover
In fact, I was exactly doing that at university many years ago. After some time, I found that I had more passion for Chinese than Japanese. So, in my case, I decided to go with Chinese and stopped studying Japanese after about half a year.
I do think that studying both at the same time is definitely doable but I think it is kind of a rational decision. I found that you really need to have some purpose for learning these languages. I always wanted to go to China and work there for some time but I did not have the same plans for Japan and Japanese. So in the end, it made more sense to me to stick with Chinese.
Also, as both of these languages are incredibly complex and very different from each other (yes, there are the Kanji but that's about it), I think if you truly want to master any of these, learning both of them at the same time is, in most cases, not beneficial.
Learning these languages will take you many many years. It's not like learning an other European language, not even close. Of course it always depends on what your native language is. But if I understood correctly, your native language is probably a European one.
In any case, good luck with your journey. And if you do have any specific questions about learning Chinese/Japanese, let me know!