Currently I am trying to solve more than 5 problems in day but I can't find any problems that will help me to achieve a great experience. So, I wish you will give your favorite problem(which is typically great for himself/herself) so that I can solve it and achieve a great foundation.
Some of my favorite problems
https://mirror.codeforces.com/contest/802/problem/E
https://mirror.codeforces.com/contest/145/problem/E
https://mirror.codeforces.com/contest/321/problem/C
https://mirror.codeforces.com/contest/1925/problem/E
https://mirror.codeforces.com/contest/375/problem/D
https://mirror.codeforces.com/contest/86/problem/D
he is a newbie you are giving him 2400s maybe add some simpler problems keep these Ill solve them but send some simpler ones