how do personal freedoms guaranteed by democracy is threated by other government forms like communism ?

Personal Freedom can only be guaranteed in a rule where the person can decide who rules.
Explanation:
In communism the state has the highest power, over the people.
That means that the state can decide when to restrict the movement of the people or to take away their personal freedom from them if the state deigns it so.
In democracy that is not possible.
The personal freedom of movement and of expression are some of the inalienable rights of a true democracy.
No matter what happens these are the rights that are enshrined to a democracy safeguarded by the elections.

Hope it help :)

Possess private property.