it might be a driver problem!!!
try to reinstall drivers and also download the latest drivers from AMD or SAPPHIRE website.
IS your PSU have enough power for your GPU???
If your HHD or SSD is OK and your old gpu did a better job in same games with same settings , the problem is drivers or PSU !!!
Try to uninstall drivers with an app named DDU ( Display Driver Uninstaller ) to uninstall the drivers completely.
After doing all of what i said , if you still have bad performance in games , tr to use benchmarking apps and compare the results with the other results in the internet ( it shouldn't be %100 same )
If you have same results as others , some thing else like your storage or CPU,etc is limiting the GPU but if your results was showing a really big gap between your card and other furys , then check the psu and drivers