Need Urgent Advice!! on alternative budget home construction methods

Part of my home which is made with rcc sheets is becoming weaker day by day. (i.e. 800sqft normal rcc roof, 300 sft(includes kitchen and bathrooms) is made of rcc sheets placed on walls.

Since, only 300sft needs to be reconstructed I would not want to pour all my money into getting pillars, roof and everything. The builder near me told it would cost me around 7lakh for demolition and construction in total.

My budget is somewhere around 1.5 -2 lakhs. The situation is tightening and I also feel stuck since it is an important part of our home that's getting weak, there's a danger of rcc sheets collapsing.

I have looked into precast construction, but I am unable to get any prices on that.

Need some insights and suggestions for an alternative method to construct that part in limited budget and which can stand for atleast 10-15 years. FYI, I live in Hyderabad.