Best Mattress to buy(UNDER 6k)

Looking to buy a good quality mattress to buy for my study room. Recently, some neighbourhood cat entered the house during rnovation and did smth(I wont elaborate, this is only plausible explanation). It's been a terrible week because I hate that bed now, can't sleep properly. What is the best mattress to buy online? I've seen some brands like Wakefit, emma, sleepyhead etc. There's stuff like MEMORY FOAM,COIR,LATEX but I can't figure out the difference b/w them and also the 100day return sounds sketchy. i have to pick one out myself because nobody else cares, so I dont wanna mess up. The measure is 74*46(not super accurate). Any help is appreciated.

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