1 – is possible (in opened portfolio) reduce the gap under preview? And also remove the thin line under it?
Sorry, I do not know what you mean by preview.
Please provide screenshot to explain the location.
2 – is possible change (slow down) the speed of gray graphs
Sorry, there is no option to set speed.
3 – is possible (in home page) use a white text in yellow counter box like a link?
Sorry, there is no option to do this.
Your question 2 and 3 requires modifications to the theme code.
We do not provide assistance in modifying theme codes.
We can only provide customization that can be done using custom css.
You may want to hire a developer from http://jobs.wordpress.net/ to assist in your customization of questions 2 and 3.