Bin packing (loading transport, scheduling), min/max of a function, least steps, least travel. One of the big applications of early computers were in ballistics tables and cut and fill for road and rail lines. Another being scheduling (classes, specialized staff, etc).
If you can't find problems to apply your algorithm knowledge to, I'd recommend compilers and 3d printing/design.
http://www.learncivilengineering.com/wp-content/uploads/2014...
https://hrcak.srce.hr/file/172575
I recommend checking out Skiena's "Algorithm Design Manual" [1] if you haven't already.
[2] https://www.algorist.com/algowiki/index.php/Chapter_10#Desig...
Then make a hash table out of the list and try finding an entry in the hash table of 100 elements and the hash table of 10 million elements.
If you want to take it further, try building an in-memory database. Benchmark how it works with and without indexes as the number of items in the database grows.