New iPhone 12 with slow wifi

I have bought my device a month ago but since then it has a huge problem of providing slow wifi speed. I moatly stay outside of my home and use LTE which is perfectly working fine but when i back home it shows the worst download speed less than 1 mb and uploading as well. This is my first iphone 🤕 in my life my previous Samsung is still running well with the same wifi I don't know what to do. I am done with reset network settings my even router ... I have reset that too. I paid alot for this phone 😔 and things are pushing me into frustration 🤬 does anyone can suggest me solution for that its updated with IOS 14.6 by default.... I need fix for that please help