Do you know any video tutorial platforms?

Depends how sophisticated you want the tutorial platforms to be...but anyway, there are two separate pieces in the question I think.

1. Tool used to record the tutorials themselves on your screen?
   • you can use video presence sites to record your sessions (like Zoom, GoToMeeting/GoToWebinar, On24, WebEx, etc.)
   • I have had success with tools like Camtasia - better for editing etc.
2. Hosting the videos you've created - again, many options here.
   • Vidyard, Youtube Channel, Vimeo, etc.
   • LMS systems: Adobe,Docebo, etc.

I would agree that Camtasia would be the best program for screen recording and editing your videos.  As far as packaging it all together, an LMS system like Adobe Captivate or https://guru.ijoomla.com/​ could be your best bet. 

Everyone here has provided some good recommendations but if you're looking to do it on the cheap (read: entirely free) and want far more flexibility at a cost of a bit of learning and time, I recommend OBS (Open Broadcaster Software).

It's used mostly by streamers but you can set it to record you directly. If you're looking to do a tutorial in one take, you can set up OBS with scenes and control them live.

It will essentially capture any part of your desktop, you can target specific windows/applications and overlay your webcam(s) with ease. If you want to take it a step further, it's easy to overlay graphics and images and dynamic content.

If you're looking for a way to track video activity in Marketo, we use Vidyard as our video platform and it works great for lead scoring and activity tracking.