Android Mobile Application Connection to a Web Host Database

I'm currently creating a mobile application for a website wherein I have to connect to a database uploaded on the web host. I have few questions on how I should start. I have knowledge in Android Eclipse but none in PHP/Web development.

Scenario:

The website is already created. It works smoothly and everything now. (It wasnt me who made it though). The databases are already uploaded on the host (hostinger.ph). I just have to connect whatever I do on the eclipse(mobile app) to the databases.

What I should do:

1. When I login in the mobile application, the mobile app should check if the entered username and password are existing in the database uploaded in the host (hostinger.ph).


2. When an admin creates an announcement for the website, it should be uploaded on the database in the host so it shows in the website homepage.


3. When an employee files for "Vacation/Sick/Emergency/Maternal/Paternal/any kind of... Leaves", it should be added in the database in the host so the Admin can view it and approve it using the mobile app.


4. Any basic viewing of files uploaded on the host.


5. 
   

   Account management (change password, user profile, etc.)

   
   

   I'm sorry that I don't have a code since I don't know how to start yet. I only have the login screen right now but I dont know where and how to transfer the username and password to the database.

   
   

My Questions:

1. Can I do it with just Android Eclipse and sqlite? Comparing my input of user and pass and do something like SELECT * FROM username/password table where the user and pass should match?


2. Can i just do the same when I want to view files? Sample I click "View Leaves", the app will then do an sql query to retrieve the file?


3. Same idea i have in account management and when an admin creates an update?

I just want to know what else do i need aside from Eclipse, sqlite. I was told I need to do a PHP Application, upload it in the host (hostinger.ph) as a backend app. Is this correct? So I can start on the right track.

Thank you so much everybody! sorry for the long post.