Backend Tweaks & SMS Integration

I need adjustments and tweaks on my website's backend and design.

Requirements:
- Add SMS integration for notifications and two-factor authentication
- Add WhatsApp symbol on website
- Modify seller panel: add and remove some details
- Fix payment gateway error

Ideal Skills:
- Proficient in backend development
- Experience in website design adjustments
- Familiar with SMS integration tools
- Knowledgeable in payment gateway systems