Hi @adnanhassan
The memory is hard mounted on the systemboard and cannot be replaced.
To upgrade the amount of memory you would have to replace the systemboard.
Here's the [https://download.lenovo.com/pccbbs/mobiles_pdf/x1_yoga_gen5_x1_carbon_gen8_hmm_en.pdf|hardware maintenance manual] for the laptop. Go to p.86 to view the procedure to remove/replace the systemboard.
Here's the parts lists for the MT [https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-x-series-laptops/thinkpad-x1-carbon-8th-gen-type-20u9-20ua/20u9/parts/display/compatible?linkTrack=Caps%3ABody_SearchProduct&searchType=4&keyWordSearch=X1%20Carbon%208th%20Gen%20-%20%28Type%2020U9,%2020UA%29%20Laptop%20%28ThinkPad%29%20-%20Type%2020U9|20U9] and [https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-x-series-laptops/thinkpad-x1-carbon-8th-gen-type-20u9-20ua/20ua/parts/display/compatible?linkTrack=Caps%3ABody_SearchProduct&searchType=4&keyWordSearch=X1%20Carbon%208th%20Gen%20-%20%28Type%2020U9,%2020UA%29%20Laptop%20%28ThinkPad%29%20-%20Type%2020UA|20UA] models, that may help. (check for the MT number on the product information label on the bottom of the laptop).
Click on ''Select Commodity - System Boards (110)'' to find the part numbers for the 110 different systemboards that are used in the laptop. If you click on the ''Specs'' link in each part you'll see the relevant specifications of the motherboard.