Because you are comparing two individuals (ik and jij), therefore you need to use the stressed form.
In English you can only do this by using intonation, in writing, you'd either use capitals or bold/italics to signal this emphasis achieved through voice. As in 'I am a man and you are too' or '... so are you'.
You have to do more than 10 random strengthening lessons (not the same ones all the time) every day for weeks on end before Duo will regild your subjects. The algorithm for determining your weak words is not as good as it's made out to be and doing fewer than 10 means you'll keep repeating the same lessons every day.
They generally speak rather fast. Actually, any foreign language sounds as if speakers were rushing as they speak, when they're actually speaking at normal speed. It's just when one is learning a language, it takes quite a long time to be able to process normal speed. Don't worry, you'll get there! I've been studying Dutch for a bit over 2 1/2 years now (Aug. 2018).
Depending on your level, I'd recommend you to start watching the news, since newsreaders speak 'fast' but very clearly. :)