Verb conjugation of "wispern" in German

On Thursday I have an appointment. If there is no other way, I'll move it. Can you meet on Tuesday, April 11, anyway? I suggest 10.30 in the morning, but I'm fairly flexible, so noon is good too.
You have to be careful when you go on summer vacation. There are many dangers but the most dangerous one is the sun itself, because if you're not careful it may harm you. People underestimate the rays.
I have not managed to contact you. And please write me only to the Vocabulix inbox and not directly to my other email addresses? When is the best time to reach you? For me anytime is good.