Wants to get knowledge about digital arts canvas designs

Could anyone give me an idea how to paint abstract paint for high digital print without having visible pixels in the picture??

It depends your printing size in Inches, and the PPI ( Pixels per inch, pixel density) of your printer.

This one is often standardized to 300ppi. Higher rare quality goes to 450ppi, and sometime large ads poster that have to be seen in distance can drop under 150ppi and lower. But if you have no idea, 300ppi is a good start.

Then, you can do the math for height and width:
Number of Pixels necessary for your canvas = Size in inch * PPI

Fortunately, the New Document and the Resize dialog in Krita can do the math for you if you enter the size and ppi.