In addition to what others have suggested, try these as well:
1. Whenever you try to speak in English, don't think in your vernacular and try to translate into English; instead, think in English and speak out. Initially, you may make mistakes, but gradually, you will improve.
2. Make sure that whenever you are with your friends and family, you speak or converse only in English. Share with them the mistakes you are making and correct them.
3. For a simple conversation, you don't need an in-depth vocabulary; commonly known English words are sufficient. Also, correct your grammatical errors by discussing them with your close friends.
4. Practice discussing your subject for a group discussion in front of a mirror at home. If you practice with a close friend who is proficient in English, they can help you improve your speaking flow and body language.
5. Read printed materials on the topic of group discussions frequently. Memorize important sections and recall them during discussions.
6. Approach the group discussion without an inferiority complex. Think that others are also like you, and you are well-prepared. Have a mindset full of confidence.
7. Listen, read, watch, recall, and present. Keep your eyes and ears open at all times.
I hope these tips help you improve your English speaking skills.
Best regards