When new clues from the diary of her long lost brother, help a young woman to solve a riddle of decades old crime, she is compelled to go to Siberia in search for her vanished family and a missing treasure.

This logline does not reveal any conflict, inner or outer. Is there an antagonist or something she must fight against.

Corridorone.

From the posts above it seams that each iteration of the logline is getting a number of consistent comments. I suggest implementing these notes as they mostly still apply to the latest draft of the logline.

Perhaps tighten a bit?

After a daughter uncovers her dead brother's diary, she scrambles from Brazil to Siberia searching for her family and her birthright fortune.

I modified - What do you think?

"Clues from lost brother diary reveal a riddle about a long-forgotten crime and put the heroine on a trail leading her to Siberia in search of her vanished family and a missing treasure"

It sounds like the two big problems with this concept are:

The translation of, the impact of the clues on the MC from book to film and a direct cause and effect relationship between the inciting incident and the goal.

In film the main plot points have to be visual. How does reading a diary visually explain that the MC is now motivated beyond doubt to take action? As inciting incidents go this is weak, is there another way the MC can be made to need to achieve her goal?

As previously mentioned no need to stick to the book page for page. When adapting a book you have to make concessions for film as you are writing for a different medium.

Secondly for the plot to make sense the plot points need to have a logical connection that necessitate each other. From the logline (and as DPG said) how does reading a diary make someone want, nay, need to go to Siberia?
Currently it doesn't, so what is the connection between the brother and Siberia? Was he an archaeologist or treasure hunter who worked there?

Lastly don't be afraid to elaborate on the plot in specific detail at these early stages of development. You are not at risk of giving away the plot when you are still trying to structure it for film. Description such as "...solve a riddle of decades old crime..." are too vague for a logline as they do not describe what happened.

Was the crime a murder? If so who was murdered? Was it a theft? If so what was stolen?

Biggest problem of the concept and logline is the goal.
Her solving the decades old crime is not part of the plot and potentially should not be in the logline. The goal is confusing, is her goal to find the criminal who did the crime or find the long lost family or find the treasure?

It can't be all three, pick one main goal for the MC to pursue and mention only that in the logline. This will help tremendously when you come to structure the plot for the film. The other goals can be subplots or objectives for her to achieve throughout the story on her way to the main goal.

Hope this helps.

thanks

Perhaps just a small change:

Clues from a family diary reveal a riddle about a long-forgotten crime and put the heroine on a trail leading her to Siberia in search of her vanished family and a missing treasure.

Thank you.
I know the theory. Please take a look not on my replies, but on my log line and tell me your opinion, and what and how to improve it. Highly appreciate.

'It will be hard to explain in one sentence since the story is complicated and twisted.'

Then you're going to have problems. However, every story has a main character, goal and conclusion, despite everything that is going on, you just have to find it and there's your logline.