Are you talking about new one unit? If so, give where you bought it.

If you talking about Huawei E3276, yes gargoyle can support this model. http://eko.one.pl/?p=openwrt-modemylte#huaweie3276 - sorry I have only polish description.

First, I have set the channel mode to Auto in my TPLink router and there are better channels but it does not automatically switch to those channels. I restarted the router but it did not work ? Any...

If you have Windows OS please install inSSIDer and give us screenshot from measurements.

I think it's time for the hammer.. Maybe you're right ;) Greetings from Poland!

but speed is not 1 GB start transfer speed at 900 MB then drop to 500 MB or 200 MB Do you mean about network speed inside?