.Net Framework 3.5 installation problem number 0x800f0954

It seems your machine can’t get the stuff he needs, is disconnected from THE INTERNET. If you work in an offline environment try this:
Mount your OS installation drive/ISO.
Run Powershell as Administrator and do

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:YOURDRIVELETTER:\sources\sxs