I am a web developer, but my designs are not upto the industry standard [on hold]

I am a web developer, but my designs are not up to the industry standard

How to improve my skill.

I want to design like these,

• https://www.instamojo.com/
• https://razorpay.com/
• https://consumers.citruspay.com/
• https://www.cashfree.com/
• https://www.digitalocean.com/
• https://in.udacity.com/ and more...

Are there any similarities between those websites?

What makes this website more attractive? Their color, font or content?

Is there any training to build those kinds of websites?