I am a lawful permeant resident in USA. Because of the current situation due to COVID-19 and the travel limitations I will be outside USA for more than 6 months from my last exit. Will that have any impact on my next entry to USA or on my record when applying for citizenship?
As far as the documentary requirements for returning to the US, the green card by itself allows you to return to the US after an absence of less than one year. You can always be asked to prove that you maintained residence in the US, no matter how long or short your absence was. (It's possible to be found to have abandoned residence even if each of your absences was less than 6 months.)
There are two impacts that happen at 6 months:
You might break "continuous residence" for naturalization purposes. An absence of between 6 months and 1 year is presumed to break continuous residence unless you provide sufficient evidence of ties to the US to overcome the presumption.
You will be considered an applicant for admission, which means you could be denied entry if you are "inadmissible" under any grounds of inadmissibility. INA 101(a)(13)(C) says that a returning permanent resident is considered to not be seeking admission unless one of several situations applies, including being out of the US for 180 days continuously, having engaged in illegal activity abroad, and a few others. That means that a permanent resident can normally return from a trip of less than 180 days even if they are "inadmissible" (as long as none of the other conditions apply). But if you have been out for more than 180 days, then you need to be careful about any grounds of inadmissibility. This is not usually a problem, as it is uncommon for a permanent resident to be "inadmissible".