Translation of retarded in German

Thanks again for your time. I attached my avatar, it is very similar to the previous one. I have guided the development of the website, and I feel free to share my knowledge with others.
As mentioned in our conversation, I will send a more detailed description about all the other exercises. As indicated previously, I believe in your technical skills and in your talent.
Thank you for your email, everything was crystal clear. We should call each other, this would be the best way. Do you have the same opinion? But I think I need more help, for example: how do you conjugate swim?