VAIO Z1 : some questions to make it work better..

Hi,

i have an old Sony VAIO Z1 (VPCZ12V5E), and i would like to rejuvenate it !
i search some tips, videos about these point :

1-/ i want to open it to clean it good : fans, keyboard..
2-/ i would like to change the Toshiba HDD with a SSD

3-/ i tried already to put windows 10 instead of windows 7... it worked but OMG ! :
the laptop speed was so slowwww !!!! i decided to put windows 7 back.
do you know why Windows 10 was so slow ?

thanks,
regards,