Could anyone help me find possible errors?

[Teacup93]

I am going to a presentation on the legalisation of cannabis in regards to medical use in Colombia. The following paragraph is a snippet of what I have written so far. Though I am not sure if it's all correct and if it's not too difficult to understand for beginner spanish speakers. I would greatly appreciate it if someone could proofread it for me and possibly point out some mistakes. Thank you!~~

''El artículo está sobre la legalización y regularización de cannabis para uso medicinal en Colombia. El presidente Juan Manual Santos firmó el decreto que fomentar la investigación y la producción de medicamentos hecho del cannabis. El decreto está sobre la licencias para la posesión de cannabis y cultivo sólo para fines médicos. El presidente declaró que la fabricación, comercialización y exportación del cannabis durante décadas se no han reglamentados. El decreto sólo permite médicos y científicos para prescriben ó usan lo sólo para fines médicos, por lo tanto no con fines recreativos.
El ministro de Salud, Alejandro Gaviria dijo que la decisión fue tomada porque el mundo cambiado culturalmente. Otros países, como Brasil, Canadá, y algunos estados de Estados Unidos ya legalizado y regulada cannabis que se utiliza para fines médicos. Con esta decisión, el gobierno quiere responder a la demanda mundial de productos medicinales basados en el cannabis.''

[Rusty]

Your first verb is incorrect. And it would sound better to use 'tratar de' instead of what you've written. The same correction can be made elsewhere.

You're missing articles in several places.

Some sentences have an infinitive where a conjugated verb is needed, like where you wrote fomentar. In this particular instance, you could use the infinitive as an object of a preposition (replace the conjunction with a preposition) and the sentence would still work, but you can't use 'que fomentar'.

In some sentences you've used a past participle instead of a past tense verb. For example, firmó is a past tense verb (preterit), while firmado is a past participle. A past participle cannot be used as a verb. It is used to form the perfect tenses (él ha firmado = he has signed) and it is used as an adjective or an adverb (los papeles firmados = the signed papers). When the past participle is used as an adjective, its ending agrees in gender and number with the noun it modifies. You used the past participle of hacer as an adjective when you wrote 'hecho', but its ending doesn't agree in number with medicamentos, the noun it is modifying. Elsewhere, you correctly used the past participle as an adjective (see productos medicinales basados).

There is one spot where a negated verb is incorrectly formulated. The same structure is also the location of one of the spots where a past participle is supposed to be paired with a conjugated form of haber to form the past perfect tense. You're missing a conjunction in that sentence, too.

After 'permite', you need a noun clause (start the clause with a conjunction) and, in that clause, your verbs need to be in the subjunctive mood, because permitir is a verb of volition. In the same clause, the direct object pronoun 'lo' needs to precede each verb. I don't know why you've added 'por lo tanto no con fines recreativos' to that sentence.

You've written 'ministro de Salud'. Both of the principal words should share the same case. You should also provide the full name of the secretary.

Convert 'fue tomada' to the pasiva refleja construction. That sentence also contains a past participle that should have been used to form a past perfect verb (add a conjugated form of haber).

Look up the name of the President of Colombia. It is misspelled.

While fixing the places where a past participle was used stand-alone, instead of being paired with a conjugated form of haber, you need to use the 'ado' ending (look at 'legalizado y regulada' - both need converted to the past perfect tense).

There are other errors, but you can start with the ones I have mentioned so far.
Post your corrected narrative and we'll point out what remains to be fixed.