so you want an app for message broad casting with whats app api i can give you this job in 3 days
please check my work and skills
i am 7+ year Experienced Senior Android (kotlin ,java) Developer.
I’ve carefully gone through your job posting.
I’m an expert PHP developer and worked on many PHP projects before. I have more than 7 years working experience in PHP.
I can show you my prior work More
There is no official Whatsapp API
You may get banned for using any 3rd Party API.
You can however simply use WhatsApps Click To Chat to send Messages. For an Example on how to do that you can have a look on HTTP GeMore