If my grandma has thyroid problems could i and what causes bad thyroid or what makes it bad?

Maybe: There are some forms of thyroid disorders that are inherited, like graves disease and hashimoto's (chronic autoimmune thyroiditis). There are different forms of thyroid dysfunction like over active and under active thyroid. They have different symptoms like fast heart rate for overactive (hyperthyroid). Thyroid cancer can also be hereditary. If you have concerns for your risk, see your doctor.

Possible: Autoimmune thyroiditis, the commonest being hashimoto's disease, does indeed have a strong genetic predisposition, more from the mom's side. Of course it will still depend on what type of thyroid problem your gm has. If you think you are experiencing symptoms of low thyroid such as hair loss, excessive fatigue, memory loss or cold intolerance, then please have your pcp check your thyroid levels.