When exactly did you first start making a significant contribution to the project?

I started making a significant contribution to the project when I gained the ability to independently implement tasks that affect the key functional parts of the application. For example, in one project, I took responsibility for the data processing module, where I implemented algorithm optimization, which improved performance by 20%. This happened after several months of studying the code and discussing with the team, when I already had a good understanding of the architecture and project requirements.