Can't download anything using play store

hello,

I need to re install waze. I tried many times using playstore but it says "download is queued" and it stays like that for hours. I tried downloading other programs and it's the same. But I can use google to surf the internet. I have motorola defy mb525. I tried turning the phone off and on again and it didn't help.

Please be very specific. I have no background knowledge

Please help,

Thanks.