Wa Alaikum Salam.
Sister I am assuming that there are no leakages in the cooling system, and all hoses, pipes, etc. are intact. In such case, you may top up with Toyota Genuine Coolant, which comes 50/50 premixed from the factory. I hope, it will suffice. If not, and there are some sort of leakages, then I fear, more expenses may be involved. First leakages will be sorted out, their causes and remedial actions, then either top-up, or complete flushing of old coolant, and filling up with new coolant.
@fastian04 Brother kindly guide the sister regarding good garage in Lahore, may be one-stop shop, where she can get everything done at reasonable charges, and in professional manner.
Then, as recommended multiple times by one of the Senior members here, Capsat Sahib, following garage will also be able to resolve your issue, IN SHA ALLAH:
Obama Car & Truck Centre, 110 Tipu Block, Garden Town, Lahore.
0321-4106898 is the contact No. First call for an appointment between 10 am to 7 pm and then visit. Diagnostic charges apply.
Whichever garage you visit, thoroughly discuss the issues with the mechanic, and as recommendation, always go for preventive maintenance, instead of reactive!
I hope, all above helps. Thank you.