A comedy film about detective agency

[Rarog]

An elderly owner of a detective agency dies. He leaves his business and large fortune to his granddaughter with whom he has scarcely or never seen before.
After the grandfather’s death his assistant (a young man) looks for the girl. But he comes at the wrong time; she is busy and very mad at him.
However the assistant succeeds to bring her to the grandfather’s house, where he shows her the grandfather’s will that has been videotaped.
The girl refuses the inheritance resolutely. But it’s not so easy because her grandfather has foreseen everything. He answers to her from the screen and then the real "live" conversation begins between them. The grandfather’s arguments are stronger therefore she concedes.
It develops that the grandfather hasn’t stop there and has recorded an entire movie library for his beloved granddaughter. In such a way a video cassette with the best advice or answer is always at hand whatever she does or asks for.
The grandfather has prepared a few test detective cases in order that his granddaughter be able to "enter the profession." The first case is a return of a stolen horse. The other one is an investigation into some machinations with wines, the girl creeps in the cellar.
Gradually the girl involves in the detective business, the new job starts to like her. The assistant helps her in all things. And finally they fall in love with each other.

[will.15]

I don't think it is what you are talking about, but the TV series Honey West a woman runs a detective agency she inherited from her father and has a male assistant around her age.

[Rarog]

The film must be in color. But thanks for your attempt to help me.