Need help with Pascal Raycaster

[YO5PEV]

Hi there! I have attached to this post a raycaster which i made in Pascal and assembly language but it has some bugs such as : 1.textures on distant walls look very inaccurate/messy; 2. Textures on wall/ceiling are buggy at viewing angles close to 0 degree and 180 degree (i think that it is a problem in the 386 assembly code); 3. The player can look through corners at some viewing angles;
Could somebody check this out and explain me what causes these bugs ? Thanks in advance.