What we do first flowchart or algorithm?

Answer 1

Flowcharts are used in designing and documenting simple processes or programs. Like other types of diagrams, they help visualize what is going on and thereby help understand a process, and perhaps also find less-obvious features within the process, like flaws and bottlenecks.
Ref : https://en.wikipedia.org/wiki/Flowchart

Answer 2

Start with algorithm. Then you can draw the flowchart.
Flowchart is a diagrammatic way of representing an algorithm. So start with the algorithm.

Answer 3

I would suggest you to take the other way because algorithms may differ based on your problem.
Make a flow chart and write down the requirements. See how are you going to solve the problem. See if a particular condition fails, in that case you can easily switch to a different algorithm.
Who knows, you might end up writing a whole new algorithm which might work just right for the problem you have to solve.
Just an opinion.