Verb conjugation of "zumbar" in Spanish

I work as an actor in the theater. I have studied English for seven years, French and Spanish for two years. Well, my level of Spanish is too low to have a good conversation, but I understand it.
Could you please read the following offers in a critical manner and confirm it before I will send it? I have also mentioned the warranty and the software in the offer, because it was requested by the customer.
Of course I understand the reasons. I live in Thun, which is not far from Bern, our capital city. How come your Spanish is so good? Have you ever been to Switzerland. You are most welcome.