salaams bro (i presume). you need to cut out the source, fair enough the fitna never stops but Allah swt gives us a simple mechanism of lowering our gaze. this is supposed to be purer for us. try and do it as much as possible.
the most important step is aquiring taqwa, fear and love, of Allah. remember the punishments associated with immodesty and of sin in general. you think these thoughts are nice but...
1.think about it for long enough and you loose all interest. its a temporary thing without meaning
2. it cannot be nice because your lord does not approve of immodesty therefore for the love of Allah it cannot be nice to you.
3. is it nice knowing the punishment these women will face due to their immodesty? associate these images with that torment. (for me, i try to see myself and them suffering in the fire whenever i have bad thoughts)
there is also the problem of sensitization, so you may feel desire over lesser levels of fitna. the best way to deal with this is giving it time. your head is just accustomed to thinking it needs this, but Allah swt must have made it possible to live quite happily without it otherwise it would not be haram. and inshallah you wont have to fight it ur whole life, come a weeks time you wont even know why you had said thoughts in the first place, inshallah
an important step is under no circumstances allow these images to run free in your head during salah. learn the translation of some of the verses of quran, an excellent investment, so you can fill your heart with the remembrance of Allah swt instead. once you can control them during salah you can start to extend your sphere of control over the rest of your life. i know its not easy but you need to be brave and ask Allah to give you the tawfiq. also never intentionally brnig the thoughts to your mind. and try to remind yourself that youve seen it all before, you can gain no benefit from seeing it again.
finally in surah baqarah v 256:
let there be no compulsion in religion: Truth stands out clear from Error: whoever rejects evil and believes in Allah hath grasped the most trustworthy hand-hold, that never breaks. And Allah heareth and knoweth all things.