Is php7 supported?

Yes, since version 4.2.0 db connection and queries are using mysqli instead of mysql extention. So the stats are working on both (php5/7), if mysqli-extention is supported by your php-version.

Are the stats running on servers with php5?

Yes, see question above.

How do I do an update if I already have a version installed??

For an update basically you only need to replace the actual web components (everything except folders "db" and "cronjob").
If you need to replace other components, there will be more information in the changelog of that version.

I use Boinctasks and want to host my running tasks on my webspace. How do I do that?

For this feature, I recommend the use of WinSCP.
Then you edit boinctasks/boinctasks_ftp.txt according to the comment and copy all files of boinctasks/ into the directory

C:\Users\%USERNAME%\AppData\Roaming\eFMer\BoincTasks\html\

Now you have to change the settings in Boinctasks and activate in

Tab "Cloud" the option "activate WWW-Update"

and change the value in

Tab "Tasks" for CPU% - and Progress% decimal to "0".

So that it also matches the colors of the Userstats, set the following colors via
"Settings -> BoincTasks Colors and Fonts -> Tasks":

green: #a6f0c8 (RGB 166 240 200) für "activ"

yellow: #fae297 (RGB 250 226 151) für "ready for execution"

blue: #95e2fb (RGB 149 226 251) für "Ready to report"

red: #f8d7da (RGB 248 215 218) für "Canceled" und "Error"

For GPU tasks the colors simply "darken" a bit. For further information on boinctasks, please refer to the help manual of boinctasks.

Can I sort the tables?

Since version 4.3.0 you can also sort the tables. For details, see the changelog to version 4.3.0.