Unfortunately you can't get the wood bright again with a bright glaze. With each paint the wood will be a little darker.
Either you grind the wood complete, so that you get the original colour of the wood, or you can also try a special powder to bleach the wood. The wood bleaching powder helps to restore the natural colour of weathered wood.
After that you can try to paint and protect the wood with a light glaze e.g. "Sikkens HLS".
The "Aufhelltechnik"/"Brighten technique" should be another method to get dark wood brighter. More detailed information you can find here: Brighten Technique