Mr. Tajammal is right do the false ceiling on first floor and if possible take the maximum advantage of roof height, take it to the maximum high level, it will be very effect effective to tackle heat,
Yes he is also correct about sanity work, we are professionals in this field so i do know very well the importance of high quality sanitary items most importantly good quality concealed pipes, invest one time and enjoy life time is the correct word can be used. Do not go for saving in this item,
Hire someone how knows very well even if you are asked to pay 50% more,