Many have been asking, well here's the answer, learn to save files from telegram with these few steps; 

Steps to Download Files Apk Games Music Video and Pdf files from Telegram 

1) tap file and wait to download 

2) tap the 3 dots at d top right corner of the file, tap "save to gallery" or downloads" 

3) that's it, you have successfully downloaded and saved d file to your device. 

 Now after doing this, you might notice a reduction in your storage space,

this is because the file has been saved twice (once in your device's telegram folder, and a second in your downloads folder).

If left alone, the file saved in the telegram folder is usually automatically deleted after three(3) days, but if you need your space urgently you can follow these easy steps;

1) Go to your device file manager and enter internal storage 

2) Once in internal storage, locate the folder named, "Telegram", and tap on it

3) Next locate the type of file, namely; audio, video, documents, and tap on the category of your file

4) Lastly, the files saved in this section are usually labeled with random alphabets/codes and not the file's actual name,

so be very careful to only delete files you have already "saved to downloads/gallery", or files no longer needed, if confused try using the file sizes to determine which is which. 

Hope this post was helpful. Leave any questions in the comment section