What kind of extracurricular should I do, which is somehow connected with theater arts/forensic science(criminal justi)?

I honestly have no idea what extracurriculars if any are associated with forensic science. However for ecs associated with theater and arts check out local programs in your community and volunteer to help out. Depending on the seriousness of the program they may not want minors but it couldn't hurt to ask if they just want someone to help out with props and such. Remember that if you are paid it still counts as an ec and if you are not you could likely file any time spent as volunteer hours. Good luck!