Our general recommendations:
Install Grammarly to see your mistakes in writing and learn to prevent them.
Take an online English test to identify problem areas.
Consider switching your role or a company to make sure you regularly have to speak English at work. For example, an outsourcing company with English-speaking customers.
Whenever you are tired try watching entertaining/relaxing videos in English with subtitles.
Some people like learning lyrics of their favorite songs in English.
Practice your English where possible.
Consider taking additional English-language classes: