Hi Gianluca,
T3 v2.0.0 come with a new T3 Bs3 Blank template which work with Bootstrap 3.
You should change the memory limit to 128MB in order to compile LESS to CSS.
And please describe your problem in detail so I could give some suggestions.
And we would recommend to use our quickstart package instead install in a exsting Joomla.
https://github.com/t3framework/t3qs/releases