Hi @Fatimah_Salman ,
Below is my demo flow:

There are several points need to be carefully treated. And we have the same DataSources and columns actually.
Flow details:
1. Firstly, you will need to add three custom dynamic content in this flow by clicking Ask in PowerApps three times:

How to click:
add three 'Compose' action and rename them like below firstly:

Then you can go to each input of them and click the Ask in PowerApps one by one and here is the result you will get, please make sure you have exactly the same result as mine or you need to create a new flow from scratch:

My Student list columns:

Then add "Get items" action and add filter query inside:

You will see that for lookup column, you need to add '/' character after the lookup column name in Student list and then you need to add the column which hold the real text value of this specific lookup column name from its original list. In my college list, the Title column hold the college name and this is why my condition here is:
college_lookup/Title
and after the eq(equal) character, you need to add the related dynamic content and also, add the ' character around it. Below is the string value of my formula:
college_lookup/Title eq '@{outputs('College')}' and department_lookup/Title eq '@{outputs('Department')}'
You can just copy and paste but make sure you have changed the lookup column names with the real lookup name value from your side.
Here is one link that you can refer to if you are still confused: Power Automate - How To Filter SharePoint Lookup Column - YouTube
Then you will receive all the students records from this IT department and you can just add "Send an email" action:

As to the survey part, it's the same logic ,you will need an additional get items action to return the survey selected from power apps.
Canvas app part:
In the button onselect property, type below code:
'flow_name'.Run(Dropdown1.Selected.Value,Dropdown1_1.Selected.Value,Dropdown1_2.Selected.Value)
Remember to keep the order of the composes in your flow here. The dropdown1 should hold the college info and the second dropdown should hold the department value, and so on.

That's all, please mark my answer if you think it answers your questions.
BR,
Hen Wang