Here is the main source of the earliest information from David Kaufmann's "Die familie Gomperz" published 1907. It is available on the Internet Archive. Their text version can be run through Google Translate. .
This page from it connects them to my ancestors in Gelderland, NL.
Who was in the Gomperz Family?

 Dutch immigrants once held fervent beliefs: Premillennialism spread at the end of the nineteenth century, Zionism soon became influential,
 and the Fundamentalist movement began around 1914. Then over one hundred years ago the Great War changed everything ...
The one hundredth year anniversary of Rev. Fles passing into glory was March 29, 2021.  Myself at Zeeland Cemetery. 

 The "Lord's Garden" web page  has an 1894 quote from Rev. Fles.
 Rev. J. I. Fles biography - the longer version had end notes.  The last link in it mentions a Zeeland RCA church. Now I'm finished adding more.
 This time I mean it (unless something big happens)!
 The same longer version but try saving word as html page.  Try to possibly catch within and store that saved result for later access via wayback machine?
Test if one image on archive is available
 The same longer version in a pdf.  If your device doesn't have Word, it might not show the many end notes.
 The published version of his story.  The article in CRC history magazine has other pictures.
 His story in a single page.  Here is a nice way to get a brief impression; wordcloud.  Here is another new one.
 A story about Rev. John Rottenberg.  I hope the short format is suitable for "this hero who gave up his life
                                                             for the sake of bringing the gospel to the Jewish people." (per Glaser)
 The same Rottenberg story, as a pdf.  A good format.

 Rev. Fles in Muskegon, perhaps around 1900 
 John and Johanna Fles 
 Rev. Fles and family, probably before 1900 
 Parsonage in Pella, IA around 1912. Minnie and Hermine, Rev. De Leeuw and Nell, Johanna, grandson John, Rev. Fles  
 Possibly in that parsonage  
 Fles had a playful side. 
  In the 1888 CRC Synod he showed his serious side. 
 Aalten NL 
 The SS Rotterdam was a year old in 1873 
 Presbyterian Church in Cedar Grove, WI. 
 Old Scholte church in Pella, IA. 
 Zeeland, MI.
Follow the road your ancestors took, and
you will find peace.
Jer. 6:16
 Zeeland anniversary party on August 31, 1887 is mentioned in the story. 
 After interurban street train reached Zeeland in 1901 
 Unknown funeral in Zeeland Cemetery from between 1900 & 1910  
 The old North Street church 
 North Street C.R.C. in Zeeland, MI. 
 First C.R.C. (in 1891 before fire) in Muskegon, MI. 
 First C.R.C. and parsonage (after fire) in Muskegon, MI. 
 The Chicago Hebrew Mission in 1891    
 Open air meeting in West side Chicago "Jewish quarter" 
 World's Fair in Chicago in 1893 
 The German Kaiser in Belgium in 1914 
 British General Allenby enters Jerusalem in 1917, during Hanukkah