Thank you very much

as Yevgeniy said ,

je crois (from verb croire) mean I believe

je pense (from verb penser) mean I think

but je crois can be also from verb croître and so it's I grow up ....

so depends the context and or if you ve the infinitiv verb form also ...

I hope it's help you !

I guess it's like "beliave" and '"think"