How can I extend y-axis in the way that line in the top don't finish sharply with the end of graph. In this case would be fine to extend y-axis to 8 or even 9, note that I can't set limit to 8 because speed value will be always different. It's only about visual effect.
Second question, also estetic, graph start with double 0, how can I delete one of them but still keep graph in same way
Without seeing your code it is difficult to understand what you have already done and how your data is structured to create the graph, is it a pandas df? it is a list of values? Also what librarys are you using. Assuming you are using matplotlib this has already been answered here How to set the y-axis limit.
Get current axis via plt.gca(), and then set its limits:
ax = plt.gca()
ax.set_xlim([xmin, xmax])
ax.set_ylim([ymin, ymax])
You could look at doing
ymax = int(round(max(list of y values)+2,0))
This would give you a ceiling of plus 2 and round it to a whole number.
The second question is just usual, from my experience, however looking at your graph you could use the above code and set the limit to be higher/lower for the x&y axis.
I fixed first problem with ymax = round(max(y))+1 but not the one with zeros, when I'm trying to use same pattern for example ax.set_xlim([1,xmax]) it's just moving my graph, I would like to keep it unchanged just make one 0 disappear, but it's not so big of a deal