Pl post a workbook
Doing side by side bars of 2 separate measures is easy enough, using the Measure Names/Measure Values fields available. Using Superstore, the layout would look something like this:
The problem is not trying to add a 3rd measure (simply selecting an additional Measure Name would achieve that), it's trying to add a measure with a different mark type and a different behavior. Initially, you might think to add the 3rd measure as a dual axis on the Rows shelf, which would let us declare a new mark type:
The problem is that when you try to change it to a line, you're only going to get 3 individual dots. The reason is because the Columns shelf is divided by discrete dimensions; each column is its own entity, so it can't really connect from one to the next. What kind of information are you trying to present? Maybe we could help you find a feasible and more effective way of visualizing it. If you can attach a packaged workbook it will give us the best handle on how to help.