In the last ten years, polar code research has piqued the interest of firms and researchers, particularly in the communication industry. Polar codes have been utilised as a coding method for the fifth-generation wireless standard (5G). However, the polar decoder does not adequately correct errors in successive cancellation (SC) decoding when dealing with short- to intermediate-length codes. However, SC decoding can correct errors more efficiently by using sequential cancellation list (SCL) decoding. The main drawback of SCL is its higher cost due to computational complexity and throughput. The present research investigates the effect of Gaussian approximation (GA) and different decoding approaches on the performance of polar codes. First, SC and SCL decoders are developed utilising amplitude shift keying modulation; a decoder using GA is then integrated. According to simulation data, the SCL, both with and without GA, exhibits a better block error rate (BLER) than SC. The maximum difference between the SCL decoder and SC decoder is 0.6 dB at BLER=0.1 for N=2048. Furthermore, at BLER=5.6 x 10-6, the SCL decoder with GA performs better than the SC decoder for block lengths, N=1024, with a maximum difference of 2.72 dB. When the polar decoder with GA is utilised, enhancements are observed in polar code performance for various list sizes and block lengths, although time complexity is increased.