Cities or urban places are very complex particularly when you investigate the topic of happiness in public spaces. Issues or variables such as center/periphery, high or middle/lower classes, population/density, industrial/commercial or tourist, secular/religious significance among other variable must be considered. Focus on one or more of these variables might help attacking the problem.

Hello Sahar,

I don't know if these links will be of any help?:

Article What makes a ‘happy city’?

“I'm always entirely happy when I'm here!” Urban blue enhancing human health and well-being in Cologne and Düsseldorf, Germany

http://www.tlu.ee/~arro/Happy%20Space%20EKA%202014/happy_urban%20blue.pdf

Article HOW IMPORTANT IS METHODOLOGY FOR T HE ESTIMATES OF T HE D ET...

Article Urban environmental quality and human well-being: Towards a ...

Article The Geography of Happiness: Connecting Twitter Sentiment and...

http://www.happycity.org.uk/wp-content/uploads/2016/10/Happy-City-Wellbeing-Measurement-A-Guide-to-Quantitative-Data-collection.pdf

Article The relationship between greenspace and the mental wellbeing...

https://www.urbandesignmentalhealth.com/journal-5---urban-form-and-mental-wellbeing.html

Very best wishes for your PhD,

Mary

Dear Researcher, the following questionnaire in a tabular form wit perfection of individuals AT DIFFERENT AGE GROUP SUCH AS 25-35 / 35- 45 / 45-55 / 55 - 65/

EACH AGE GROUP CAN BE UP TO 100 - 150 PERSON - MALE AND FEMALE IN EQUAL PROPORTION OF 50% AND 50%.

The dynamic methodologies to evaluate happiness and mental health would be as follows:-

A perfect evaluation can be done with the work out and can easily identify the number of people happy in various levels and their mental state of happiness in different levels.

I have done my best to share knowledge with you.

Forgive me if anything is not Correct.

Thanks

https://iopscience.iop.org/article/10.1088/1757-899X/618/1/012078/meta

This link is kind of the reverse of happiness but can give some ideas