X- axis label Orientation

I have been looking to change the label orientation on X-axis. Is there any way to do so?
If not, the data label of X-axis is too large and unclear. Is there any way to fix that?

You can use TGaxis::ChangeLabel:
https://root.cern/doc/master/classTGaxis.html#a8ef5ba035d846add3902cd714336eaac
e.g. if it’s a histogram: h->GetXaxis()->ChangeLabel(...

See also this example.