constitution of read and gene region (IGV)
You have asked quite a few questions here. I will try to answer a subset of them. 

To answer your question, I started by going to the UCSC genome browser, and selected the BLAT from the tools dropdown menu. Then passing your primer sequences as queries, we can clearly see where they map to the reference genome.



Looking at the figure above, I can guess that your data comes from a targeted sequencing experiment (exome, or gene panel, etc); where you have primers around each exon of EGFR on two strands, on 5' end of exon sequence on each strand (think about DNA polymerase acting in PCR to amplify the number of DNA molecules before sequencing).

Regarding the adapter, I am not sure which read you are referring to. Can you clarify please? 

About percentage of mapped vs unmapped reads, you can use bamtools. 

Example Usage:

/user/me/src/bamtools/bin/bamtools-2.3.0 stats -insert -in my-sequence-file.bam

Example output:

Total reads:       103277668

Mapped reads:      90088436     (87.2293%)

Forward strand:    58136735     (56.2917%)

Reverse strand:    45140933     (43.7083%)

Failed QC:         6529806      (6.32257%)

Duplicates:        0    (0%)

Paired-end reads:  103277668    (100%)

'Proper-pairs':    87439672     (84.6646%)

Both pairs mapped: 87910438     (85.1205%)

Read 1:            51638834

Read 2:            51638834

Singletons:        2177998      (2.10888%)

Average insert size (absolute value): 6317.39

Median insert size (absolute value): 301