Bar Graph Category

Hi Md_asgar_786 
This happens because there isn't enough space for the string in the hierarchy, which is longer than the height of the bars at the level below.

You can see in my example that some of the names are shown properly and in the cases of fewer bars in the next hierarchies it looks like in your image :

To deal with this issue you can resize the space between the bars :

My recomendation
In such cases, since we don't have many design options here, I recommend using a matrix with conditional formatting. You'll get a much more organized and aesthetically pleasing result

The pbix with the examples is attached

Thanks for sharing the solution, but my requirement is same like you have done in the below visual:
Level 1:

How to reduce the length of the Bar, then we show both category as well as sub-category.

Level 2:

In the 2nd level visual which you have created you are showing categoryName as well as firstName as per your pbix file. that how you have achieved and as well as in Y axis you are showing category name also for a group  that also i would like to undertand how you have done it.

Ritaf1983