hi @Ben-00-38 the charts in power apps are a bit limited if you done have access to power bi but luckily there are some workarounds.
Let's deal with your second question first. You must group your data by the "user" column to get the cumulative data
ClearCollect(colHisto,AddColumns(yourDatasource,"user","users"),"cumulative result",Sum(users,CA)))
Here a new collection (colHisto) is being created by grouping the user columns as users and add a column called cumulative result which totals the values from CA.
Let's through that into a bar chart. as you can see all the users scores are grouped.

Now let's flip the chart.
Power Apps don't allow you to flip it, well at least not to my knowledge but you can get away by using a gallery.
Add a vertical gallery and set the
Items = colHisto
Add a label (lblUser) and set the
Text = ThisItem.user
Add a rectangular (Rectangle1) shape and set its
Width = (Parent.Width - (lblUser.Width+220)) * ThisItem.'cumulative result'/ Max(colHisto,'cumulative result')
Add some variance to the shape's color,
Fill = Switch(true,ThisItem.name = "User 0", Yellow,ThisItem.name = "User 1", LightGreen,ThisItem.name = "User 2", LightBlue ,WhiteSmoke)
The reult:

The x poistion of the cumulative label,
X = Rectangle1.X + Rectangle1.Width + 5 and the
Text = ThisItem.'cumulative result'
you can adjust the scale by incorporating the min value etc but i willleave you to do that if you wish to.
Hope it helps