I would like to thank the people and the teams that surround me.

First of all, a huge thank you goes to the Packt team. You are amazing in supporting this process and striving for quality and delivery. Thank you, Nikhil, for being with me all this time and providing me with all the necessary and just-in-time feedback.

My Meetrics team not only gave me an invaluable moral support but also helped me with the book's content. Safi did a UI/UX investigation and helped me with the initial mockups for the application. Jan Christian made a thorough technical review of the book. His deep technical understanding helped me improve the code and his attention to tiny details helped me improve my writing and my way of expressing and approaching some subjects. Thanks a lot!

My EdEra team has given me great help and support. My friends from EdEra Berlin, thank you for helping me with ideas, thank you for listening and brainstorming with me, and thank you for helping me with CSS. Oleg, Jenia, and Nadia, you are awesome!

How can you create a great application if you are a total noob in design? You can't! But if you have friends who can help you with design, you are the happiest person on Earth. Thank you, Vanessa, for helping me with the application design and thank you, Filipe for helping me with its implementation. Thank you, Carina, for the fantastic logo!

Thank you, Marina for your friendship and for being the first person who heard the idea of ProFitOro and encouraged me to go ahead.

Thank you, mom and dad, for being with me and believing in me. Thank you my wonderful brother, Ilia, for being an inspiring example for me. Thank you Ukraine, for being with me in my heart. Thank you Portugal, for being my second Ukraine. Thank you Berlin, for being such a great city that helps people in being creative.

Thank you, my little Taissa, for being the reason for me to work and try my best. I know that you are proud of me, and this is something that drives me.

Thank you, my beloved husband, Rui, for reviewing all my chapters. Thank you for your patience. Thank you for your love.