I have spent 15 years working as a software engineer, but I have taken some time off for other projects in the last 18 months, supporting myself with part-time shifts for a start-up that has grown considerably in that time. Now I’d like to get back to full-time work and secure a position at the company, but am unsure how to negotiate this with the head of department. How can I propose a change in my current contract, without compromising the relationships and goodwill I‘ve built at the firm?