Translation of subestimar

We arrived at my Casa, a private home with an extra place that the family rented. I sat down and they gave me a drink. They explained me that they wanted me to stay at another house for some reason.
Please write me from your home as soon as your are back. My Spanish is better than that of most Americans, but my English is worse than that of most people here. It is a strange position that I am in.
The ice blocks that usually break off during the summer started already to break off in spring due to the Global warming. The glaciers in general were loosing volume as we were told and as we could see.