Problem with summer in VHDL
You can find and fix the syntax errors. They are usually quite simple.
In this case, you may need a better VHDL compiler to help you diagnose them ...
ghdl ( https://github.com/ghdl/ghdl documented at https://ghdl.readthedocs.io/en/latest/) reports
ghdl -a aritmetico.vhd
aritmetico.vhd:35:8:error: invalid use of UTF8 character for '

presumably at F1&lt;= ‘0’ which should be F1&lt;= '0'
This sort of thing happens quite often if you copy/paste code from the PDF version of a textbook, and can be quite difficult to spot. Some type setter, unaware of the strict nature of VHDL syntax, decides to make the text look pretty...
There appear to be other errors too, but all in good time...