The first signs of genus Homo in Silesia date to between 230,000 and 100,000 years ago. The Silesian region between the upper Vistula and upper Oder was the northern extreme of the human penetration at the time of the last glaciation. The anatomically-modern human is estimated to have arrived in Silesia about 35,000 years ago. Subsequently, Silesia was inhabited by people who belonged to changing archaeological cultures in the Stone, Bronze and Iron Ages, and the ethnic identity of whose cannot currently be determined. The civilization of Old Europe undoubtedly included Silesia. In the late Bronze Age, the Lusatian culture (in the past, variously speculated to be either 'pre-Germanic', Proto-Slavic, Thracian, Karpo-Dacian or Illyrian) covered Silesia. Later, the Scythians and Celts (the tribes of Boii, Cotini and Osi) are known to have played a role within the Silesian territory. Still later Germanic tribes migrated to Silesia, possibly from Northern Germany or Scandinavia.
Most likely...meaning they assume it but have no concrete data for the times for germanic tribes in document.
Not sure what you are trying to aim at ... it is all easily searchable asn some is part of big historical events in the region.
But it seems ethnically Silesia was originally informally cut small pieces and diverse. Not heavily german, even had celts. When it became formally "Silesia" the bulk was under control from Czech(Morovian-Bohemian) before passing to the Polish in dynasty era.
The history shows Germanic tribes were hovering and immigrating through the east part before settling further south and were not a heavy portion of population until a large influx of Walloons in 12th century and the 13th century had open invitation for settlers from Germany. Then they slowly displaced the local population by the numbers. But all and all it looks like it was all polish in upper and split german/czech in lower for more than a single century. Works by Jan Potocki could help you with the tribes/ethnicities documents in first century.
::Genes, Peoples, and Languages" Scientific American, November 1991
:::The Celtic Encyclopedia, Vol. 1, Universal Publishers, May 1, 1998