Yes you can do good even if your English is not that good. You must try to improve that. Can I know about which group discussion and personal Interview you are asking about? You must have valid points to make in group discussion and during personal interview you must talk softly and try to give answer in simple English and must abstrain from using difficult words. You can do well in those just focus on important topics and valid points, try to practice before it from many sites available online.

Hey Anushka,

For cracking Group Discussion and Personal Interview of any college, you need to have a strong command over English language. The main objective for conducting GD and PI while taking admission is only to check your verbal skills and presence of mind, whether you have fluency in spoken English or not.

You need not worry for this as learning to have a command over English language might seem to be a big deal but it is not so. This will take some practice. Use simple language but try and have some sort of a structure in your answer. Don't jump from one point to another randomly.

Start reading. Read as much as you can. If reading is new to you then start with HT City newspaper. Start conversing  in English. Don't be scared that you would be laughed upon. Start writing, as most colleges prefer WAT over GD now days it will be of  twice the benefit. Start with Public Speaking.
Also listen to what is it that you are being asked very carefully. If you don't understand something, clarify. NEVER beat around the bush!

Keep practicing, you will definitely then have good spoken English and would be able to crack GD and PI of any college and will ace it.

Hope this helps.

Good Luck!