The interview was done over a span of 2 months and didn't even bother to get back. During this period the founder gave many excuses for delay and was mostly not genuine in nature. He tried to ask for ideas he can personally use, I would advise not to give it coz that is what they feed on from people and take advantage of who is interviewing with them.
The salary offer was given over an excel file on WhatsApp which is extremely unprofessional in nature. And when an attempt was made to negotiate on the offer he goes completely AWOL. From what I've heard salaried pay, in general, is way below average. If you're looking for compensation this is the last place to look at but your intent is to learn and experiment with ideas you'll find that here.