When I use paragraph text and type quite large text, it goes beyond the bottom border of the bound box and part of the text is no longer visible. I want to make the whole text automaticalystay within the border and when it exceeds the size of the given border its font size just decreases so it fits perfecrly
This is not possible with paragraph text. You have to use regular line text and apply expressions based on a virtual bounding box and using sourceRectAtTime(). There's a million posts on this on how to auto-wrap and fit multi-line text in templates using this method, so do a search here on this forum or the web in general.
I was looking around and some people say it's possible to make with one master text layer, where you input your text and then it separates into individual text layers, but I really don't know how to do that. I don't need to wrap around text, I just need to make sure the pasted text stays wihin defined area and if needed creates automatically new lines and scales down the font.
I've cheked every related video on youtube, they all are about box wraping, which I don't need