Need help repairing a leaking toilet flush

Hi, I have a toilet in my bathroom that has a leaking flush mechanism. It’s causing the water to run continuously, and I’d like someone experienced to come and fix it properly. The flush handle feels a bit loose, and I suspect the internal parts might need replacing. Ideally, I’d like the repair done quickly as the constant running is increasing my water bill. Please bring any necessary tools or parts if possible. Looking forward to your help!