Based on your friend's message, it looks like Lisa's cat (referred to as "Tatze") has given birth to 3 kittens. You can congratulate her by mentioning the 3 new kittens in your message. Here's a suggestion for how you might congratulate her: "Congratulations on the new additions to your family! Three little kittens must be so exciting and adorable. Wishing you all the best with your new furry friends!"