URL Shortening Website (API, React.js)

It was a great experience working on this. Usually I am a perfectionist, but I felt like I should just submit it or else it will take forever :D. After all, there are many other projects I need to work on, this is just my first one. I think it is decent, except for minor differences between it and the original. Please tell me your opinion and point out the mistakes or even better methods I should've used. It really helps :D