You can upload only those photos that you hold the rights of. If you upload not just your own photos, but the photos of others (e.g. relatives or friends), you have to have the right for distribution on the internet.
For photographs of other photographers you need a written contract. By uploading a photo you put it up to public criticism. Think about which photo you choose. It is not necessary to publish only the best works. Upload a photo and ask if it is not successful in the description text or the first note, how this photo can do better. This is available in the fotocommunity. In all cases, however, you need to adjust to a public debate and also authorize (factually correct negative) criticism. It is not allowed to upload pornographic, glorifying violence or politically extremist material. German law applies here.