what lens would you advice to canon 600d for lots of focus and blurred background?

Any lens of 50mm or longer in size. Like some manufactures make a 60mm, and longer.
Be sure to use the widest lens opening (aperture). I personally use a 200mm lens and a Tiffen warm soft filter (F3), for this purpose with my portraits especially of older folks (age 50 & older).

As you can see many ways to "attack" this situation

You just have to try various lenses and filters(in my case) to see what pleases you.

I just noticed that you added for weddings. My recommendation is check out the Canon web site. Along with lens descriptions they give most popular uses. And then read all the reviews you can find on the Canon site, B&H's site and Amazon. This will give you a "feel' for what will be good for YOU!
www.usa.canon.com/home (Phone number) 1-800-OK-CANON

www.bhphotovideo.com 1-800-854-5575

www.adorama.com 1-800-223-2500

https://www.amazon.com/

Good Luck!

50mm f/1.8

http://keerok-photography.blogspot.com/2011/05/how-to-blur-background.html