Ok so when does E3 start? I see in the internet 16-18, but Bethesda shows starts 14??

It starts at 7 pacific time; 1900 for PT in 24hrs.

Convert to your proper time zone.

E3 proper starts on the 16th, but big companies have their own showcases prior to the main show. Bethesda's is on the 14th.

When does the very first starts?

The very first what? Bethesda's show is on the 14th (this Sunday) at 7 pm pacific time (GMT -8). There are more publisher showcases on Monday, and then the E3 floor opens on Tuesday.

IGN has a pretty good schedule here:http://m.ign.com/wikis/e3/E3_2015_Live_Streams_and_Press_Conferences

We have a thread for discussing Bethesda at E3 this year, and E3 in general. http://www.gamesas.com/topic/1518982-e3-2015-thread/

The above linked IGN schdeule explains when things are happening.