Tableau could handle as much data as possible, as there is no limit for it. Tableau has no limit as such not even stated in its manual regarding this. But the only thing that should be kept in mind is that Tableau is limited by the database it's connected to.
If you are looking for a good course on Tableau, then have a look at Intellipaat’s Tableau certification course which provides you instructor-led course with projects and exercises to build your hands-on experience.
Also, do take a look at our YouTube video on Tableau training, to get started.