Water ingress though window frames is a very common issue but can easily be resolved.
Remove all old loose sealant etc from around the wall and frame junction/ I Beam.
Clean down the area, ensure its dust free.
Apply flexible polyurethane sealant NOT SILICONE! along the frame and wall junction.
Use masking tape to ensue neat lines and property protection.
Use a finger dipped in soapy water to help with the smooth pulling of the lines.
Golden rule NEVER USE SILICONE for this area it cannot take the UV and the movement.