I start working in this software and hardware company 2 years ago as an Android developer. There were 4 developers in the team; 3 working on the server and me. Since the very beginning it was very easy to notice my skills were far above them so I start to make recommendations and helping them. After a few months my responsibility became working with the server, the database, writing REST APIs, developing the iOS app, Android app, write front-end website, etc..
Suddenly I have to do everything. So I mention to my boss my responsibilities were too much and I was afraid if one day I get sick, who will do my job? My boss told me not to worry.
So after 2 years I decided to quit, I gave 40 days notice to my boss and agreed he will find my replacement. After 30 days, there is no replacement and there is no evidence my boss is really looking for someone. This Monday my boss transferred to my bank account 2 times my salary and he sent me an email saying it's a way to say thanks for all my effort. Tuesday he asked my if I can work extra hours even above the legal working hours in a new project (that I estimate will take at least 40 days to do)..
Here is the problem: he just sent me that money because he wants me to work extra hours. How can I tell my boss that I will not work extra hours and after the my last day I will not do anymore work for this company?