Fix MultiThreading Contention Issues in Console Application

I have a C# Console Application that has multi-threading already added to it. The issue is that only one thread is actually performing tasks at once, when they should all be running and executing at the same time. I need someone who is very familiar with multithreading and fixing contention issues. Must speak English well and be able to work on it now via Teamviewer. Please let me know your experience with such work in description. I only would like to pay $25 for this, should only take about an hour or so.