Why my office selects next character when I want to add space or edit words?

Hi
I have a problem when I try to edit words or adding space between characters. It automatically selects characters and this forces me to rewrite the whole of the word again because I cannot add for example a space between two characters.

Press Ins key.

From what you say it looks like you have set overwrite mode rather than insert mode. At the bottom of the display there is the status line. Near the center it shows the language. To the right of this there is a box that will be empty for insert mode or show “Overwrite” for overwrite mode. Clicking on this box will toggle the mode. The insert key on the keyboard will also toggle the mode.