Why my range of wireless network in laptop decreased?

Hi @afshiyankhan

It could be due to a loose antenna cable connection to the WLAN card on the motherboard.

Here's an image taken from the image in Step.4 of the ifixit Acer Aspire E5-573G Hard Drive Replacement guide, that shows the location of the WLAN card and the two antennas connected to the card.

Open the laptop and check if the cables are securely connected to the card.

I highly recommend that if you try this that you disconnect¹ the battery cable from the motherboard as soon as the back cover has been removed first, before doing any further checks in the laptop. This will minimize any possible electrical problems from occurring to the board. (See Step.7 of the Acer Aspire E5-573G Battery Replacement guide). Also take heed of the warning in Step.6 regarding the speaker wiring).

Also make sure that you don't touch any components that you don't have to, so as to prevent any possible ESD damage from occurring to them whilst working inside the laptop.

¹ You don't have to remove the battery, simply disconnect it. Don't forget to reconnect the cable once you start to close it up again.

(click on image)