.NET Performance Optimization Needed

I already have the full source code for a desktop .NET application and I’m happy with its functionality, but it feels sluggish. What I’m looking for is a focused performance pass aimed purely at speed—no new features or bug-hunting, just making the existing code run faster... (Budget: ₹600 - ₹1500 INR, Jobs: .NET 5.0/6, .NET Core, C# Programming, C++ Programming, Software Development)