Security is very important and specialy on Internet. To secure your webpages you can use Let's Encrypt to issue certificates and allow you to use SSL protocol in communication. It's free and very easy!
Non-Profit Certificate Authority for SSL certificates
You can issue certificates for any domain valid for 90 days
Certbot utility which can renew certificates for any system
Most popular language for programming. Java is very robust, stable and with rich ecosystem of tools and set of coding standards. With Java Virtual Machine (JVM) you can run it almost everywhere and also with Android you can program your app for mobile phones.
Java can run everywhere due to its JVM implementation
Huge amount of tutorials and strable libraries
For small or big projects - Java SE, Java EE, Spring